Biyernes, Marso 21, 2014

The Urinary System

Urinary System Anatomy

Kidneys
KidneysThe kidneys are a pair of bean-shaped organs found along the posterior wall of the abdominal cavity. The left kidney is located slightly higher than the right kidney because the right side of the liver is much larger than the left side. The kidneys, unlike the other organs of the abdominal cavity, are located posterior to the peritoneum and touch the muscles of the back. The kidneys are surrounded by a layer of adipose that holds them in place and protects them from physical damage. The kidneys filter metabolic wastes, excess ions, and chemicals from the blood to form urine.
Ureters
The ureters are a pair of tubes that carry urine from the kidneys to the urinary bladder. The ureters are about 10 to 12 inches long and run on the left and right sides of the body parallel to the vertebral column. Gravity and peristalsis of smooth muscle tissue in the walls of the ureters move urine toward the urinary bladder. The ends of the ureters extend slightly into the urinary bladder and are sealed at the point of entry to the bladder by the ureterovesical valves. These valves prevent urine from flowing back towards the kidneys.
Urinary Bladder
The urinary bladder is a sac-like hollow organ used for the storage of urine. The urinary bladder is located along the body’s midline at the inferior end of the pelvis. Urine entering the urinary bladder from the ureters slowly fills the hollow space of the bladder and stretches its elastic walls. The walls of the bladder allow it to stretch to hold anywhere from 600 to 800 milliliters of urine.
Urethra
The urethra is the tube through which urine passes from the bladder to the exterior of the body. The female urethra is around 2 inches long and ends inferior to the clitorisand superior to the vaginal opening. In males, the urethra is around 8 to 10 inches long and ends at the tip of the penis. The urethra is also an organ of the male reproductive system as it carries sperm out of the body through the penis.
The flow of urine through the urethraUrinary system cross-secrion is controlled by the internal and external urethral sphincter muscles. The internal urethral sphincter is made of smooth muscle and opens involuntarily when the bladder reaches a certain set level of distention. The opening of the internal sphincter results in the sensation of needing to urinate. The external urethral sphincter is made of skeletal muscle and may be opened to allow urine to pass through the urethra or may be held closed to delay urination.

Urinary System Physiology

Maintenance of Homeostasis
The kidneys maintain the homeostasis of several important internal conditions by controlling the excretion of substances out of the body. 
  • Ions. The kidney can control the excretion of potassium, sodium, calcium, magnesium, phosphate, and chloride ions into urine. In cases where these ions reach a higher than normal concentration, the kidneys can increase their excretion out of the body to return them to a normal level. Conversely, the kidneys can conserve these ions when they are present in lower than normal levels by allowing the ions to be reabsorbed into the blood during filtration. (See more about ions.)
     
  • pH. The kidneys monitor and regulate the levels of hydrogen ions (H+) and bicarbonate ions in the blood to control blood pH. H+ ions are produced as a natural byproduct of the metabolism of dietary proteins and accumulate in the blood over time. The kidneys excrete excess H+ ions into urine for elimination from the body. The kidneys also conserve bicarbonate ions, which act as important pH buffers in the blood.
     
  • Osmolarity. The cells of the body need to grow in an isotonic environment in order to maintain their fluid and electrolyte balance. The kidneys maintain the body’s osmotic balance by controlling the amount of water that is filtered out of the blood and excreted into urine. When a person consumes a large amount of water, the kidneys reduce their reabsorption of water to allow the excess water to be excreted in urine. This results in the production of dilute, watery urine. In the case of the body being dehydrated, the kidneys reabsorb as much water as possible back into the blood to produce highly concentrated urine full of excreted ions and wastes. The changes in excretion of water are controlled by antidiuretic hormone (ADH). ADH is produced in the hypothalamus and released by the posterior pituitary gland to help the body retain water.
     
  • Blood Pressure. The kidneys monitor the body’s blood pressure to help maintain homeostasis. When blood pressure is elevated, the kidneys can help to reduce blood pressure by reducing the volume of blood in the body. The kidneys are able to reduce blood volume by reducing the reabsorption of water into the blood and producing watery, dilute urine. When blood pressure becomes too low, the kidneys can produce the enzyme renin to constrict blood vessels and produce concentrated urine, which allows more water to remain in the blood.
Filtration
Inside each kidney are around a million tiny structures called nephrons. The nephron is the functional unit of the kidney that filters blood to produce urine. Arterioles in the kidneys deliver blood to a bundle of capillaries surrounded by a capsule called aglomerulus. As blood flows through the glomerulus, much of the blood’s plasma is pushed out of the capillaries and into the capsule, leaving the blood cells and a small amount of plasma to continue flowing through the capillaries. The liquid filtrate in the capsule flows through a series of tubules lined with filtering cells and surrounded by capillaries. The cells surrounding the tubules selectively absorb water and substances from the filtrate in the tubule and return it to the blood in the capillaries. At the same time, waste products present in the blood are secreted into the filtrate. By the end of this process, the filtrate in the tubule has become urine containing only water, waste products, and excess ions. The blood exiting the capillaries has reabsorbed all of the nutrients along with most of the water and ions that the body needs to function.
Storage and Excretion of Wastes
After urine has been produced by the kidneys, it is transported through the ureters to the urinary bladder. The urinary bladder fills with urine and stores it until the body is ready for its excretion. When the volume of the urinary bladder reaches anywhere from 150 to 400 milliliters, its walls begin to stretch and stretch receptors in its walls send signals to the brain and spinal cord. These signals result in the relaxation of the involuntary internal urethral sphincter and the sensation of needing to urinate. Urination may be delayed as long as the bladder does not exceed its maximum volume, but increasing nerve signals lead to greater discomfort and desire to urinate.
Urination is the process of releasing urine from the urinary bladder through the urethra and out of the body. The process of urination begins when the muscles of the urethral sphincters relax, allowing urine to pass through the urethra. At the same time that the sphincters relax, the smooth muscle in the walls of the urinary bladder contract to expel urine from the bladder.
Production of Hormones
The kidneys produce and interact with several hormones that are involved in the control of systems outside of the urinary system.
  • Calcitriol. Calcitriol is the active form of vitamin D in the human body. It is produced by the kidneys from precursor molecules produced by UV radiation striking the skin. Calcitriol works together with parathyroid hormone (PTH) to raise the level of calcium ions in the bloodstream. When the level of calcium ions in the blood drops below a threshold level, the parathyroid glands release PTH, which in turn stimulates the kidneys to release calcitriol. Calcitriol promotes the small intestine to absorb calcium from food and deposit it into the bloodstream. It also stimulates the osteoclasts of the skeletal system to break down bone matrix to release calcium ions into the blood.
     
  • Erythropoietin. Erythropoietin, also known as EPO, is a hormone that is produced by the kidneys to stimulate the production of red blood cells. The kidneys monitor the condition of the blood that passes through their capillaries, including the oxygen-carrying capacity of the blood. When the blood becomes hypoxic, meaning that it is carrying deficient levels of oxygen, cells lining the capillaries begin producing EPO and release it into the bloodstream. EPO travels through the blood to the red bone marrow, where it stimulates hematopoietic cells to increase their rate of red blood cell production. Red blood cells contain hemoglobin, which greatly increases the blood’s oxygen-carrying capacity and effectively ends the hypoxic conditions.
     
  • Renin. Renin is not a hormone itself, but an enzyme that the kidneys produce to start the renin-angiotensin system (RAS). The RAS increases blood volume and blood pressure in response to low blood pressure, blood loss, or dehydration. Renin is released into the blood where it catalyzes angiotensinogen from the liver into angiotensin I. Angiotensin I is further catalyzed by another enzyme into Angiotensin II.

    Angiotensin II stimulates several processes, including stimulating the adrenal cortex to produce the hormone aldosterone. Aldosterone then changes the function of the kidneys to increase the reabsorption of water and sodium ions into the blood, increasing blood volume and raising blood pressure. Negative feedback from increased blood pressure finally turns off the RAS to maintain healthy blood pressure levels.
Ipinaskil ni sa Walang komento:

The Endorine System

The Endocrine System


The endocrine system is all about hormones.  So far the glands we’ve gone over, such as the liver, pancreas, etc, all have ducts that lead into openings.  The endocrine glands don’t have ducts and have a whole different process.  This collection of small, ductless glands secrete messenger molecules called hormones directly into the bloodstream.  By dumping the hormones straight into the blood stream, they could just circulate throughout the cardiovascular system and end up at a target organ.  That specific hormone will look for receptors on some specific organ and act upon that organ to trigger a physiological response.  So that’s how hormones are going to work at this level of your understanding.
Side note:This idea that we have specifically glands dedicated to secreting hormones is an old perspective.  Nowadays researchers are realizing the whole idea of an endocrine-specific gland is not accurate because EVERY organ in your body secretes hormones.   Every cell in the body secretes hormones.  This includes your bones, skin, etc. We know a lot about health but nothing nearly as much as we still have yet to learn. (In other words, we don’t know shit, relatively speaking.)
Just a quick rundown of the picture above: These are your major endocrine organs.  We’ve already talked about the pineal gland, hypothalamus, and we’ve also mentioned pituitary.  We didn’t get into the pituitary gland in detail yet but we will.  We have heard of the thyroid gland.  Thymus, we’ll talk about that in a little bit.  Adrenal glands, we’ve heard of those before when we talked about parasympathetic division of the ANS.  We’ve talked about pancreas and its exocrine function (the digestion part).  We’ve already talked about ovaries and testes in the reproductive system.  So that’s why it’s ideal to go over the endocrine system last.
Above: This is an explanation of how hormones, in general, are released and do their job, which is usually to trigger another organ to release another hormone.  Then that new hormone will circulate and come back to the original endocrine gland so that the gland doesn’t have to send anymore hormones out.  This is anegative feedback loop.  A positive feedback loop is the reverse, in that it builds up stuff in the bloodstream and triggers the endocrine gland to get even more of that hormone.  No matter how an endocrine gland is stimulated, hormone secretion is always controlled by these feedback loops.

The Pituitary Gland

Notice the pituitary has an anterior and posterior lobe.  This is our master gland.  Hypothalamus has control over the pituitary, so it’s not really the master, but it’s called that for some reason.  The anterior lobe has 5 different types of endocrine cells that are going to make/release at least 7 different known hormones.  Some of the hormones are still unknown.  Endocrinology is a very active field in terms of research for figuring out stuff like this to this day.

Anterior Lobe of Pituitary Gland

The pituitary could actually produce more than 7, but we know at least these:
Growth hormone stimulates growth of the entire body but especially those epiphyseal plates (located at the ends of the long bones in a child were those plates/strips made of cartilage, and that was where you could make the bone longer.  The cartilage would grow, get eaten away and get replaced with bone and repeat.) So the pituitary gland secretes growth hormone that goes to the plates to grow and then suddenly you need a new wardrobe.
Thyroid-stimulating hormone signals the thyroid to produce thyroid hormone.
Adrenocorticotropic hormone (Adreno sounds like adrenals, cortico sounds like cortex, -tropic means having an affinity for/being attracted to) so this is a hormone that stimulates the adrenal cortex to get it to secrete corticosteroids.
Melanocyte-stimulating-hormone.  We’ve heard melanocyte before in regards to the skin.  This stimulates those melanocytes but in the studies this hormone doesn’t significantly stimulate the production of melanin for humans specifically but in other animals it does.  Strangely enough of it suppresses your appetite and increases sexual arousal.
Gonadotropins (sound like gonads, so it’s in regards to the testes or ovaries and -tropis means being attracted to, so these hormones are going to tell the gonads to tell something.)  These are follicle stimulating hormones and luteinizing hormones (LH) which stimulates the maturation of sex cells (Sperms or eggs) and secrete sexual hormones (testosterone or estrogen/progesterone).
Prolactin stimulates milk production.
The hypothalamus that controls the pituitary is going to secrete releasing hormones itself so that it could get the anterior lobe of the pituitary to release things.  Or it could secrete inhibitory hormones to turn off secretion of anterior lobe hormones.

The posterior lobe of the pituary gland

The posterior lobe of the pituary is actually an extension of brain tissue containing the axons that store and release hormones produced in the hypothalamus and has a very different structure from the anterior lobe even though it’s considered to be a separate organ.  Released from those neurons are antidiuretic hormones (diuretic is in regards to getting rid of water, which the kidneys are going to do) that act at the kidneys to help keep water.  Oxytocin gets smooth muscle to contract in the uterus.  More specifically, these uterine contractions happen during childbirth and after birth this hormone tells the breast tissue to eject milk into those lactiferous sinuses.

Thyroid gland

Not too much here as far as anatomy goes.  Thyroid cartilage is right in the front of the gland. We have a right and left lateral lobe.  The isthmus is the connection of the two lobes in the middle.  You could see the relationship with the aorta and how close they run.
The thyroid is a big heavy-duty, physiology topic, as most of the endocrine glands are, so let’s look at it a little.
Follicular cells produce the actual thyroid hormone (aka T3 and T4).  We’ve all heard of iodine before, right?  That thyroid hormone carries iodine in it and is responsible for regulating your basal metabolic rate.
Parafollicular cells (para meaning next to) are going to produce calcitonin which is related to calcium.This lowers the calcium levels in your body by acting on the kidneys.  Calcium happens to be one of the ions the kidney can release back in the body or keep it to go to the uterine system.  We need calcium for the bone tissue and for heart muscle contraction.

The parathyroid glands

Below: If we turn the neck structure around and look from the back, we will see the larnygopharynx, which is behind the larynx.  So when we look for the thyroid gland in this posterior view, we see the two lateral lobes of it with the pharynx on top.  On the back of those lobes we have these tiny glands called parathyroid glands.  The parathyroid cells are going to release parathyroid hormone which helps increase calcium concentration in the blood. Another type of cell called an oxyphil cell, whose function still has not been determined yet, exists there.

Adrenal glands

We already talked about the medulla of the adrenal gland so we’re going to talk about the cortex which is the outer layer.  Remember the medulla portion is part of the sympathetic nervous system and it secretes epinephrine and norepinephrine.  The adrenal cortex forms the bulk of the gland and it secretes corticosteroid hormones which have a relationship to the stuff secreted by the medulla because they do very similar things.
Aldosterone eventually gives us testosterone.  Cortisol and androgens also contribute to testosterone production.  If you have trauma with blood loss occurring, those adrenals will go nuts to keep your heart pumping when it senses your blood pressure is dropping.  If you have an infection the adrenals will help it fight with all its might.  Fasting is pretty stressful on the body too and the adrenal cortex will definitely kick in to keep everything revved up.  Stress also moves that entire adrenal gland.  All adrenal hormones help cope with danger, terror or stress.

Pineal gland

We’ve talked about the pineal gland a little before when we talked about the epithalamus but here’s a little more detail.  Pinealocytes secrete melatonin, a hormone that regulates circadian rhythms.  This process is also under the influence of the hypothalamus.  There are calcium ions located between the cells known as “Pineal sand” (aka corpora arenacea).  Because the calcium is radiopaque, the pineal gland is used as a landmark to identify other brain structures in x-rays.

Pancreas

The pancreas contains both endocrine and exocrine cells.  The exocrine cells are acinar cells that secrete digestive enzymes.  The endocrine cells of the pancreas are a separate groups of cells, scattered throughout the pancreas, so it’s not like there’s a separate section like with the adrenals with a cortex and medulla.  All these cells are mixed in together and the endocrine cells are located in the Pancreatic islets (or the Islets of Langerhans).  We have about a million of those islets and in them we have alpha cells and beta cells.
The beta cells secrete insulin that goes into the bloodstream all over the body and functions in all of your cells to allow glucose in so the cells can digest it.
Alpha cells secrete hormone called glucagon which signal the liver to release its storage of glucose in the form of glycogen (which is just a starch; glycogen is a bunch of glucoses stuck together to make a starch) because you need some glucose for something like, if you haven’t ate for a while or you need a burst of energy.

Thymus

This is in the chest sitting on top of the trachea.  The thymus is really working more so during childhood and really by the time you hit 40 it has been completely replaced by fatty tissue.  The thymic hormonesstimulate the development and maturation of T-lymphocytes, a specific type of white blood cell in the lymphatic system.  You’re exposed to most of your diseases for the first time during your childhood and that is when you’re building up your immunity.  So that thymus is working aplenty during the childhood, developing t-lymphocytes, but when you are an adult you aren’t exposed to too many new things.  You may be exposed to a different strain of a cold or flu virus but in general it’s most of the same stuff by the time you hit 40.

Testes and ovaries

These glands are under the control of the pituitary gland.  We’ve talked about these before about how they produce sperm and eggs.  In between those cells that are becoming the actual sex cells are interstitial cells (that means in between) that are responsible for secreting hormones for our sexual lives.
In the testes, interstitial cells secrete mostly testosterone, which is a type of androgen.  Thetestosterone influences the formation of sperm (in seminiferous tubules) and develops your secondary sex characteristics like your public hair, axillary hair, facial hair and growing those reproductive organs during puberty and maintaining them into adulthood.
In the ovaries, those interstitial cells are called follicle cells (some turn into corpus luteum) and secrete a different version of androgen called estrogen and progesterone.  Progesterone (P for Prepare) prepares the uterus for pregnancy.  Estrogen does the same thing testosterone does for the male, it helps produce pubic and axillary hair (no facial hair), develop and maintain the sexual organs.
Ipinaskil ni sa Walang komento:

The Nervous System

The Human Central Nervous System

The central nervous system is made up of the                                                                                             
The spinal cord
The brain
  • receives sensory input from the spinal cord as well as from its own nerves (e.g., olfactory and optic nerves)
  • devotes most of its volume (and computational power) to processing its various sensory inputs and initiating appropriate — and coordinated — motor outputs.

White Matter vs. Gray Matter

Both the spinal cord and the brain consist of
In the spinal cord, the white matter is at the surface, the gray matter inside.
In the brain of mammals, this pattern is reversed. However, the brains of "lower" vertebrates like fishes and amphibians have their white matter on the outside of their brain as well as their spinal cord.

The Meninges

Both the spinal cord and brain are covered in three continuous sheets of connective tissue, the meninges. From outside in, these are the
  • dura mater — pressed against the bony surface of the interior of the vertebrae and the cranium
  • the arachnoid
  • the pia mater
The region between the arachnoid and pia mater is filled with cerebrospinal fluid (CSF).

The Interstitial Fluid of the Central Nervous System

The cells of the central nervous system are bathed in a fluid, called cerebrospinal fluid (CSF), that differs from that serving as the interstitial fluid (ISF) of the cells in the rest of the body.
  • Cerebrospinal fluid leaves the capillaries in the choroid plexus of the brain.
  • It contains far less protein than "normal" because of the blood-brain barrier, a system of tight junctions between the endothelial cells of the capillaries. (This barrier creates problems in medicine as it prevents many therapeutic drugs from reaching the brain.)
  • CSF flows uninterrupted throughout the central nervous system
    • through the central cerebrospinal canal of the spinal cord and
    • through an interconnected system of four ventricles in the brain.
CSF returns to the blood through lymphatic vessels draining the brain.
In mice, the flow of CSF increases by 60% when they are asleep. Perhaps one function of sleep is to provide the brain a way of removing potentially toxic metabolites accumulated during waking hours.

The Spinal Cord


31 pairs of spinal nerves arise along the spinal cord. These are "mixed" nerves because each contain both sensory and motor axons. However, within the spinal column,
  • all the sensory axons pass into the dorsal root ganglion where their cell bodies are located and then on into the spinal cord itself.
  • all the motor axons pass into the ventral roots before uniting with the sensory axons to form the mixed nerves.
The spinal cord carries out two main functions:
  • It connects a large part of the peripheral nervous system to the brain. Information (nerve impulses) reaching the spinal cord through sensory neurons are transmitted up into the brain. Signals arising in the motor areas of the brain travel back down the cord and leave in the motor neurons.
  • The spinal cord also acts as a minor coordinating center responsible for some simple reflexes like the withdrawal reflex.
The interneurons carrying impulses to and from specific receptors and effectors are grouped together in spinal tracts.

Crossing Over of the Spinal Tracts

Impulses reaching the spinal cord from the left side of the body eventually pass over to tracts running up to the right side of the brain and vice versa. In some cases this crossing over occurs as soon as the impulses enter the cord. In other cases, it does not take place until the tracts enter the brain itself.

The Brain

The brain of all vertebrates develops from three swellings at the anterior end of the neural tube of the embryo. From front to back these develop into the
  • forebrain (also known as the prosencephalon — shown in light color)
  • midbrain (mesencephalon — gray)
  • hindbrain (rhombencephalon — dark color) The human brain is shown from behind so that the cerebellum can be seen.
The human brain receives nerve impulses from
  • the spinal cord and
  • 12 pairs of cranial nerves
    • Some of the cranial nerves are "mixed", containing both sensory and motor axons
    • Some, e.g., the optic and olfactory nerves (numbers I and II) contain sensory axons only
    • Some, e.g. number III that controls eyeball muscles, contain motor axons only.
Link to table listing the cranial nerves

The Hindbrain

The main structures of the hindbrain (rhombencephalon) are the
  • medulla oblongata
  • pons and
  • cerebellum

Medulla oblongata

The medulla looks like a swollen tip to the spinal cord. Nerve impulses arising here
  • rhythmically stimulate the intercostal muscles and diaphragm — making breathing possible [More]
  • regulate heartbeat
  • regulate the diameter of arterioles thus adjusting blood flow. [More]
The neurons controlling breathing have mu (µ) receptors, the receptors to which opiates, like heroin, bind. This accounts for the suppressive effect of opiates on breathing. [Discussion] Destruction of the medulla causes instant death.

Pons

The pons seems to serve as a relay station carrying signals from various parts of the cerebral cortex to the cerebellum. Nerve impulses coming from the eyes, ears, and touch receptors are sent on the cerebellum. The pons also participates in the reflexes that regulate breathing.
The reticular formation is a region running through the middle of the hindbrain (and on into the midbrain). It receives sensory input (e.g., sound) from higher in the brain and passes these back up to the thalamus. The reticular formation is involved in sleep, arousal (and vomiting).

Cerebellum

The cerebellum consists of two deeply-convoluted hemispheres. Although it represents only 10% of the weight of the brain, it contains as many neurons as all the rest of the brain combined.
Its most clearly-understood function is to coordinate body movements. People with damage to their cerebellum are able to perceive the world as before and to contract their muscles, but their motions are jerky and uncoordinated.
So the cerebellum appears to be a center for learning motor skills (implicit memory). Laboratory studies have demonstrated both long-term potentiation (LTP) and long-term depression (LTD) in the cerebellum.

The Midbrain

The midbrain (mesencephalon) occupies only a small region in humans (it is relatively much larger in "lower" vertebrates). We shall look at only three features:
  • the reticular formation: collects input from higher brain centers and passes it on to motor neurons.
  • the substantia nigra: helps "smooth" out body movements; damage to the substantia nigra causes Parkinson's disease.
  • the ventral tegmental area (VTA): packed with dopamine-releasing neurons that The VTA seems to be involved in pleasure: nicotine, amphetamines and cocaine bind to and activate its dopamine-releasing neurons and this may account — at least in part (see below)— for their addictive qualities.
Link to discussion of how various psychoactive chemicals act on synapses within the central nervous system.
The midbrain along with the medulla and pons are often referred to as the "brainstem".

The Forebrain

The human forebrain (prosencephalon) is made up of
  • a pair of large cerebral hemispheres, called the telencephalon. Because of crossing over of the spinal tracts, the left hemisphere of the forebrain deals with the right side of the body and vice versa.
  • a group of structures located deep within the cerebrum, that make up the diencephalon.

Diencephalon

We shall consider four of its structures: the

The Cerebral Hemispheres

Each hemisphere of the cerebrum is subdivided into four lobes visible from the outside:
  • frontal
  • parietal
  • occipital
  • temporal
Hidden beneath these regions of each cerebral cortex is
  • an olfactory bulb; they receive input from the olfactory epithelia.
    Link to discussion of olfaction.
  • a striatum; they receive input from the frontal lobes and also from the limbic system (below). At the base of each striatum is a
  • nucleus accumbens (NA).The pleasurable (and addictive) effects of amphetamines, cocaine, and perhaps other psychoactive drugs seem to depend on their producing increasing levels of dopamine at the synapses in the nucleus accumbens (as well as the VTA).
    Discussion
  • a limbic system; they receives input from various association areas in the cerebral cortex and pass signals on to the nucleus accumbens. Each limbic system is made up of a:
    • hippocampus. It is essential for the formation of long-term memories.
      Link to role of the hippocampus
      in long-term potentiation.
    • an amygdalaThe amygdala appears to be a center of emotions (e.g., fear). It sends signals to the hypothalamus and medulla which can activate the flight or fight response of the autonomic nervous system.
      In rats, at least, the amygdala contains receptors for
      • vasopressin whose activation increases aggressiveness and other signs of the flight or fight response;
      • oxytocin whose activation lessens the signs of stress.
      The amygdala receives a rich supply of signals from the olfactory system, and this may account for the powerful effect that odor has on emotions (and evoking memories).

Mapping the Functions of the Brain

It is estimated that the human brain contains some 86 billion (8.6 x 1010) neurons averaging 10,000 synapses on each; that is, almost 1015 connections. How to unravel the workings of such a complex system?
Several methods have been useful.

Histology

Microscopic examination with the aid of selective stains has revealed many of the physical connections created by axons in the brain.

The Electroencephalograph (EEG)

This device measures electrical activity (brain "waves") that can be detected at the surface of the scalp. It can distinguish between, for example, sleep and excitement. It is also useful in diagnosing brain disorders such as a tendency to epileptic seizures.

Damage to the Brain

Many cases of brain damage from, for example,
  • strokes (interruption of blood flow to a part of the brain)
  • tumors in the brain
  • mechanical damage (e.g., bullet wounds)
have provided important insights into the functions of various parts of the brain.
Example 1:
Battlefield injury to the left temporal lobe of the cerebrum interferes with speech.
Example 2: Phineas P. Gage
In 1848, an accidental explosion drove a metal bar completely through the frontal lobes of Phineas P. Gage. Not only did he survive the accident, he never even lost consciousness or any of the clearly-defined functions of the brain. However, over the ensuing years, he underwent a marked change in personality. Formerly described as a reasonable, sober, conscientious person, he became — in the words of those observing him — "thoughtless, irresponsible, fitful, obstinate, and profane". In short, his personality had changed, but his vision, hearing, other sensations, speech, and body coordination were unimpaired. (Similar personality changes have since been often observed in people with injuries to their prefrontal cortex.)
The photograph (courtesy of the Warren Anatomical Museum, Harvard University Medical School) shows Gage's skull where the bar entered (left) and exited (right) in the accident (which occurred 12 years before he died of natural causes in 1861).

Stimulating the exposed brain with electrodes

There are no pain receptors on the surface of the brain, and some humans undergoing brain surgery have volunteered to have their exposed brain stimulated with electrodes during surgery. When not under general anesthesia, they can even report their sensations to the experimenter.
Experiments of this sort have revealed a band of cortex running parallel to and just in front of the fissure of Rolando that controls the contraction of skeletal muscles. Stimulation of tiny spots within this motor area causes contraction of the muscles.
The area of motor cortex controlling a body part is not proportional to the size of that part but is proportional to the number of motor neurons running to it. The more motor neurons that activate a structure, the more precisely it can be controlled. Thus the areas of the motor cortex controlling the hands and lips are much larger than those controlling the muscles of the torso and legs.
A similar region is located in a parallel band of cortex just behind the fissure of Rolando. This region is concerned with sensation from the various parts of the body. When spots in this sensory area are stimulated, the patient reports sensations in a specific area of the body. A map can be made based on these reports.
When portions of the occipital lobe are stimulated electrically, the patient reports light. However, this region is also needed for associations to be made with what is seen. Damage to regions in the occipital lobe results in the person's being perfectly able to see objects but incapable of recognizing them.
The centers of hearing — and understanding what is heard — are located in the temporal lobes.

CT = X-ray Computed Tomography

This is an imaging technique that uses a series of X-ray exposures taken from different angles. Computer software can integrate these to produce a three-dimensional picture of the brain (or other body region). CT scanning is routinely used to quickly diagnose strokes.

PET = Positron-Emission Tomography

This imaging technique requires that the subject be injected with a radioisotope that emits positrons.
  • water labeled with oxygen-15 (H215O) is used to measure changes in blood flow (which increases in parts of the brain that are active). The short half-life of 15O (2 minutes) makes it safe to use.
  • deoxyglucose labeled with fluorine-18. The brain has a voracious appetite for glucose (although representing only ~2% of our body weight, the brain receives ~15% of the blood pumped by the heart and consumes ~20% of the energy produced by cellular respiration when we are at rest). When supplied with deoxyglucose, the cells are tricked into taking in this related molecule and phosphorylating it in the first step of glycolysis. But no further processing occurs so it accumulates in the cell. By coupling a short-lived radioactive isotope like 18F to the deoxyglucose and using a PET scanner, it is possible to visualize active regions of the brain.
The images above (courtesy of Michael E. Phelps from Science 211:445, 1981) were produced in a PET scanner. The dark areas are regions of high metabolic activity. Note how the metabolism of the occipital lobes (arrows) increases when visual stimuli are received.
Similarly, sounds increase the rate of deoxyglucose uptake in the speech areas of the temporal lobe.
The image on the right (courtesy of Gary H. Duncan from Talbot, J. D., et. al., Science 251: 1355, 1991) shows activation of the cerebral cortex by a hot probe (which the subjects describe as painful) applied to the forearm (which forearm?).

Most cancers consume large amounts of glucose (cellular respiration is less efficient than in normal cells so they must rely more on the inefficient process of glycolysis). Therefore PET scanning with 18F-fluorodeoxyglucose is commonly used to monitor both the primary tumor and any metastases.

MRI = Magnetic Resonance Imaging

This imaging technique uses powerful magnets to detect magnetic molecules within the body. These can be endogenous molecules or magnetic substances injected into a vein.

fMRI = Functional Magnetic Resonance Imaging

fMRI exploits the changes in the magnetic properties of hemoglobin as it carries oxygen. Activation of a part of the brain increases oxygen levels there increasing the ratio of oxyhemoglobin to deoxyhemoglobin.
The probable mechanism:
  • The increased demand for neurotransmitters must be met by increased production of ATP.
  • Although this consumes oxygen (needed for cellular respiration),
  • it also increases the blood flow to the area.
  • So there is an increase — not a decrease — in the oxygen supply to the region, which provides the signal detected by fMRI.

Magnetoencephalography (MEG)

MEG detects the tiny magnetic fields created as individual neurons "fire" within the brain. It can pinpoint the active region with a millimeter, and can follow the movement of brain activity as it travels from region to region within the brain.
MEG is noninvasive requiring only that the subject's head lie within a helmet containing the magnetic sensors.
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The Circulatory System


THE CIRCULATORY SYSTEM AND LYMPHATIC SYSTEM

 


Most of the cells in the human body are Not in direct contact with the external environment.  The circulatory system acts as a transport service for these cells.   Two fluids move through the circulatory system: Blood and Lymph.  The blood, heart, and blood vessels form the Cardiovascular System.  The lymph, lymph nodes and lymph vessels form the Lymphatic System.  The Cardiovascular System and the Lymphatic system collectively make up the Circulatory System.

OBJECTIVES:

 List the parts of the circulatory system.  Describe the structure and function of the human heart.   Trace the flow of blood through the heart and body.  Distinguish between arteries, veins, and capillaries in terms of the structure and function. Distinguish between pulmonary circulation and systemic circulation. Describe the structure and function of the lymphatic system
1. Higher animals, including humans, usually have a CLOSED CIRCULATORY SYSTEM, meaning it is repeatedly cycled throughout the body.
2. It was in 1628, when the English physician William Harvey showed that BLOOD Circulated throughout the body in one-way Vessels.
3. According to Harvey, Blood was pumped out of the Heart and into the Tissue through ONE TYPE OF VESSEL and back to the Heart through ANOTHER TYPE OF VESSEL.  The Blood, in other words, moved in a CLOSED CYCLE through the body.
4. BLOOD IS THE BODY'S INTERNAL TRANSPORTATION SYSTEM.
5. PUMP BY THE HEART, BLOOD TRAVELS THROUGH A NETWORK OF VESSELS, CARRYING MATERIALS SUCH AS OXYGEN, NUTRIENTS, AND HORMONES TO AND WASTE PRODUCTS FROM EACH OF THE HUNDRED TRILLION CELLS IN THE HUMAN BODY.
6. BLOOD, THE HEART, AND BLOOD VESSELS MAKE UP THE CARDIOVASCULAR SYSTEM.
 
 
 
 
 
THE HEART
1. The Central Organ of the Cardiovascular System is the HEART.
2. THE HEART IS A HOLLOW, MUSCULAR ORGAN THAT CONTRACTS AT REGULAR INTERVALS, FORCING BLOOD THROUGH THE CIRCULATORY SYSTEM.
3. The Heart is cone-shaped, about the size of a Fist, and is located in the Thoracic Cavity between the Lungs directly behind the Sternum (Breastbone).  The Heart is tilted so that the APEX (the pointed end) is oriented to the Left.
4. The walls of the Heart are made up of Three Layers of Tissue.
    A.  The Outer and Inner Layers are EPITHELIAL TISSUE.
    B. The Middle Layer (The walls of the four chambers of the Heart) is CARDIAC MUSCLE TISSUE CALLED THE MYOCARDIUM.
5. CARDIAC MUSCLE TISSUE IS NOT UNDER CONSCIOUS CONTROL OF THE NERVOUS SYSTEM.
6. Cardiac Muscle Tissue has a rich supply of Blood, which ensures that it gets plenty of Oxygen.
7. There is also a special connection between Cells that allow Impulses to travel from one cell to another.  The Cells that make up the Cardiac Muscle Tissue are loaded with MITOCHONDRIA, (POWERHOUSE OF THE CELL), guaranteeing the each Cell has a constant supply of ATP.
8. Our Hearts Contract or Beat about once every second of every day of our lives.   The heart beats more than 2.5 million times in an average life span.  The only time the Heart gets a Rest is Between Beats.
HOW THE HEART WORKS
1. The Heart can be thought of as TWO PUMPS sitting side by side.  The Human Heart, with a Right Atrium and Right Ventricle, as well as a Left Atrium and Left Ventricle, essentially has TWO Separate Hearts inside one. (Figure 47-1)
2. The RIGHT SIDE of the Heart pumps Blood From The BODY INTO THE LUNGS, WHERE OXYGEN POOR BLOOD (DEOXYGENATED, USUALLY SHOWN IN BLUE) GIVES UP CARBON DIOXIDE AND PICKS UP OXYGEN.
3. The LEFT SIDE of the Heart pumps OXYGEN RICH BLOOD (OXYGENATED, USUALLY SHOWN IN RED) FROM THE LUNGS TO THE REST OF THE BODY EXCEPT THE LUNGS.
4. The Heart is Enclosed in a Protective Membrane Sac called the PERICARDIUM.   The Pericardium surrounds the heart and secretes a fluid that Reduces Friction as the heart beats.
5. Our Heart has FOUR CHAMBERS: (Figure 47-1)
A.  The UPPER CHAMBERS of the Heart are the RIGHT AND LEFT ATRIA (ATRIUM), RECEIVE BLOOD COMING INTO THE HEART.
B. The LOWER CHAMBERS are the RIGHT AND LEFT VENTRICLES, PUMP BLOOD OUT OF THE HEART.  The Left Ventricle is the Thickest chamber of the heart because it has to do most of the work to pump blood to all parts of the body.
6. Vertically Dividing the Right and Left sides of the Heart is a Common Wall called the SEPTUM. The Septum Prevents the Mixing of Oxygen-poor and Oxygen-rich Blood.
THE RIGHT SIDE OF THE HEART (FROM BODY TO LUNGS, DEOXYGENTATED BLOOD -BLUE)
1. Oxygen-Poor Blood from the body enters the Right side of the Heart through TWO large blood vessels called VENA CAVA.
2. The SUPERIOR (UPPER) Vena Cava brings Blood from the UPPER PART OF THE BODY TO THE HEART.
3. The INFERIOR (LOWER) Vena Cava brings Blood from the LOWER PART OF THE BODY TO HE HEART.
4. Both VENA CAVA EMPTY INTO THE RIGHT ATRIUM.  When the Heart Relaxes (Between Beats), pressure in the circulatory system causes the Atrium to fill with blood.
5. When the Heart CONTRACTS, Blood is squeezed from the RIGHT ATRIUM INTO THE RIGHT VENTRICLE through flaps of tissue called a ATRIOVENTRICULAR (AV) VALVE, that prevents blood from flowing back into the Right Atrium.
6. The valve that separates the Right Atrium and Ventricle is called the TRICUSPID VALVE.
7. THE GENERAL PURPOSE OF ALL VALVES IN THE CIRCULATORY SYSTEM IS TO PREVENT THE BACKFLOW OF BLOOD.  They also ensure that BLOOD FLOWS IN ONLY ONE DIRECTION.
8. THE SPECIFIC PURPOSE OF THE TRICUSPID VALVE IS TO PREVENT BACKFLOW OF BLOOD FROM THE RIGHT VENTRICLE TO THE RIGHT ATRIUM WHEN THE RIGHT VENTRICLE CONTRACTS.
9. When the Heart CONTRACTS a second time, Blood in the RIGHT VENTRICLE IS SENT THROUGH THE A SEMILUNAR (SL) VALVE KNOWN AS THE PULMONARY VALVE INTO THE  PULMONARY ARTERIES TO THE LUNGS.  These are the Only Arteries to carry Oxygen-Poor Blood.   At the base of the Pulmonary Arteries is a valve (Pulmonary Valve) that prevents blood from traveling back into the Right Ventricle.
THE LEFT SIDE OF THE HEART  (FROM LUNGS TO BODY, OXYGENATED BLOOD-RED)
1. Oxygen-Rich Blood leaves the Lungs and Returns to the Heart by way of Blood Vessels called the PULMONARY VEINS.  These are the only Veins to carry Oxygen-Rich Blood.
2. Returning Blood enters the LEFT ATRIUM, IT PASSES THROUGH flaps of tissue called a ATRIOVENTRICULAR (AV) VALVE to the LEFT VENTRICLE.
3. The valve that separates the Left Atrium and Ventricle is called the MITRAL VALVE or BICUSPID VALVE.
4. FROM THE LEFT VENTRICLE, BLOOD IS PUMPED THROUGH A SEMILUNAR (SL) VALVE CALLED THE AORTIC VALVE INTO THE AORTA ARTERY THAT CARRIES IT TO EVERY PART OF THE BODY EXCEPT THE LUNGS.
5. At the base of the Aorta is a Valve (Aortic Valve) that prevents blood from flowing back into the Left Ventricle.
THE HEARTBEAT (CARDIAC CYCLE)
1. The Cardiac Cycle is the Sequence of events in one heartbeat.  In its simplest form, the cardiac cycle is the Simultaneous Contraction of the TWO Atria, followed a fraction of a second latter by the Simultaneous Contraction of the TWO Ventricles.
2. The Heart consists of Muscle Cells that contract in Waves.  When the first group is Stimulated, they in turn stimulate Neighboring Cells. Those cells Stimulate more cells.  This chain reaction continues until all cells Contract.  The wave of activity spreads in such a way that the Atria and the Ventricles contract in a Steady Rhythm.
3. A Heartbeat has two Phases:
    A.  Phase 1 - SYSTOLE is the term for CONTRACTION. Occurs when the Ventricles contract, closing the AV Valves and opening the SL Valves to pump blood into two major vessels leaving the heart.
    B. Phase 2 - DIASTOLE is the term for RELAXATION. Occurs when the Ventricles relax, allowing the back pressure of the blood to closed SL Valves and opening AV valves.
4. The Cardiac Cycle also creates the HEART SOUNDS: each heartbeat produces TWO Sounds, often called LUBB-DUP, that can be heard with a stethoscope.
5. The First sound, the Loudest and Longest, is caused by the Ventricular Systole (Contraction) closing the AV Valves.
6. The Second sound is caused by the closure of the Aortic and Pulmonary Valves (SL).
7. If any of the Valves do not close properly, an extra sound called a HEART MURMUR may be heard.
8. Although the Heart is a SINGLE MUSCLE, it does NOT Contract in a Single motion.   The Contraction spreads over the Heart like a WAVE.
9. The Wave BEGINS in a Small Bundle of Specialized Heart Muscle Cells embedded in the RIGHT ATRIUM CALLED THE SINOATRIAL NODE (SA). (Figure 47-3)
10. The SA Node is the Natural PACEMAKER of the Heart.  It initiates each Heartbeat and sets the PACE for the HEART RATE.  (Figure 47-3)
11. The impulse spreads from the Pacemaker through the Cardiac Muscle Cells in the Right and Left Atrium, causing BOTH Atria to Contract almost Simultaneously.
12. When the impulse INITIATED by the SA Node reaches Another special area of the Heart known as  the ATRIOVENTRICULAR (AV) NODE. The AV Node is located in the Septum between the Right and Left Ventricles. The AV Node Relays the electrical impulse to the muscle cells that make up the Ventricles. The Ventricles Contract almost Simultaneously a Fraction of a second after the Atria, COMPLETING ONE FULL HEARTBEAT.
13. These Contractions causes the Chambers to Squeeze the Blood, Pushing it in the proper direction along its path.
14. The Heart Initiates its Own Stimulation from the Sinoatrial Node and Atrioventricular Node, and Does NOT require Stimulation from the Nervous System.
15. The Autonomic Nervous system does influence Heart Rate.  The Sympathetic Nervous System INCREASES HEART RATE and the Parasympathetic Nervous System DECREASES IT.
16. For most of us, at REST our Heart Beats between 60 and 80 beats per minute.   During Exercise that can increase to as many as 200 beats per minute.
BLOOD VESSELS  (ARTERIES, VEINS AND CAPILLARIES)
1. The Circulatory System is known as a CLOSED SYSTEM because the blood is contained within either the Heart or Blood Vessels at all times.
2. The blood Vessels that are part of the Closed Circulatory System of humans from a vast network to help keep the Blood flowing in One Direction.
3. After the Blood leaves the Heart, it is pumped through a network of Blood Vessels to different parts of the body.
4. The Blood Vessels that form this network and are part of the CIRCULATORY SYSTEM ARE THE ARTERIES, CAPILLARIES, AND VEINS.
5. With the exception of Capillaries and tiny Veins, Blood Vessels have WALLS made of THREE LAYERS OF TISSUE, that provides for a combination of Strength and Elasticity:   (Figure 47-4)
    A.  THE INNER LAYER IS EPITHELIAL TISSUE.
    B. THE MIDDLE LAYER IS SMOOTH MUSCLE TISSUE.
    C.  THE OUTER LAYER IS CONNECTIVE TISSUE.
ARTERIES AND ARTERIOLES (SMALL ARTERIES)
1. Arteries carry blood from the HEART TO CAPILLARIES AND THE REST OF THE BODY.  (Figure 47-4)
2. The Walls of Arteries are generally THICKER than those of Veins.
3. The Smooth Muscle Cells and Elastic Fibers that make up the Walls help make Arteries Tough and Flexible.  This enables Arteries to withstand the high pressure of blood as it is pumped from the Heart. The force that blood exerts on the walls of blood vessels is known as BLOOD PRESSURE.
4. EXCEPT FOR THE PULMONARY ARTERIES, ALL ARTERIES CARRY OXYGEN-RICH BLOOD.
5. The Artery that carries Oxygen-Rich Blood from the LEFT VENTRICLE to all parts of the body, EXCEPT THE LUNGS, is the AORTA.
6. THE AORTA WITH A DIAMETER OF 2.5 cm, IS THE LARGEST ARTERY IN THE BODY.
7. As the Aorta travels away from the Heart, it branches into smaller Arteries so that all parts of the body are supplied.
8. THE SMALLEST ARTERIES ARE CALLED ARTERIOLES.
CAPILLARIES
1. ARTERIOLES BRANCH INTO NETWORKS OF VERY SMALL BLOOD VESSELS CALLED CAPILLARIES. (Figure 47-5)
2. IT IS IN THE THIN-WALLED (ONE-CELL IN THICKNESS) THAT THE REAL WORK OF THE CIRCULATORY SYSTEM IS DONE.
 
3. The Walls of the Capillaries consist of only one layer of cells, making it easy for Oxygen and Nutrients to DIFFUSE FROM THE BLOOD INTO THE TISSUE.
4. Forces of Diffusion drive CO2 and waste products from the tissue into the Capillaries.
5. Capillaries are extremely NARROW; Blood Cells moving through them must pass in Single file.
 
 
 
 
VEINS
1. THE FLOW OF BLOOD MOVES FROM CAPILLARIES INTO THE VEINS. (Figure 47-6)
2.  Veins form a system that COLLECTS Blood from every part of the Body and CARRIES it Back to the HEART.
3. The smallest Veins are called VENULES.
4. LIKE ARTERIES, VEINS ARE LINED WITH SMOOTH MUSCLE.  Vein walls are thinner and less elastic than Arteries.  Veins though are more FLEXIBLE and are able to stretch out readily.
5. This flexibility reduces the Resistance the flow of blood encounters on its way back to the Heart.
6. Large Veins contain Valves that maintain the one direction flow of Blood.  This is important where Blood must flow against the Force of Gravity. (Figure 47-7)
7. The flow of Blood in Veins is help by Contractions of Skeleton Muscles, especially those in the legs and arms.  When muscles contract they squeeze against Veins and help force Blood Toward the Heart.
PATTERNS OF CIRCULATION
1. Blood moves through the body in a continuous pathway, of which there are TWO MAJOR PATHS; THE PULMONARY AND SYSTEMIC CIRCULATION. (Figures 47-8 & 9)
2. THE PULMONARY CIRCULATION CARRIES BLOOD BETWEEN THE HEART AND THE LUNGS.  THIS CIRCULATION BEGINS AT THE RIGHT VENTRICLE AND ENDS AT THE LEFT ATRIUM.   (Figure 47-8)
3. Oxygen-Poor blood is pumped out of the Right Ventricle of the Heart into the Lungs through the Pulmonary Arteries.  These are the only Arteries in the Body to Carry Deoxygenated Blood.
4. Blood returns to the Heart through the Pulmonary Veins, the only Veins to carry oxygen-rich blood.
5. THE LUNGS ARE THE ONLY ORGANS DIRECTLY CONNECTED TO BOTH CHAMBERS OF THE HEART.
6. THE SYSTEMIC CIRCULATION, STARTS AT THE LEFT VENTRICLE AND ENDS AT THE ATRIUM, CARRIES BLOOD TO THE REST OF THE BODY.  (Figure 47-9)
7. Oxygen-rich blood leaving the Heart passes through the Aorta and into a number of Arteries that supply blood to every part of the body.
8. SYSTEMIC CIRCULATION SUPPLIES EACH MAJOR ORGAN WITH BLOOD, INCLUDING THE HEART.
9. The Heart receives its supply of Blood from a PAIR of CORONARY ARTERIES leading from the Aorta.  Blood enters into Capillaries that lead to Veins through which blood returns to the Right Atrium.
 
10. The Systemic System can be divided into THREE SUBSYSTEMS: (Figure 47-9)
    A. CORONARY CIRCULATION - SUPPLIES BLOOD TO THE HEART.
    B. RENAL CIRCULATION - SUPPLIES BLOOD TO THE KIDNEYS.   Nearly one-forth of the blood that is pump into the Aorta by the Left Ventricle flows to the Kidneys.  The Kidneys Filter Waste From the Blood.
    C. HEPATIC PORTAL CIRCULATION - Nutrients are picked up by capillaries in the small intestines and are transported to the Liver.  Excess nutrients are stored in the Live for future needs.  The Liver receives oxygenated blood from a large Artery that branches of the Aorta.
BLOOD PRESSURE
1. Blood moves through our Circulation System because it is under Pressure.
2. This Pressure is caused by the Contraction of the Heart and by Muscles that surround Blood Vessels.
3. A MEASURE OF FORCE THAT BLOOD EXERTS AGAINST A VESSEL WALL IS CALLED BLOOD PRESSURE.
4. Blood Pressure is Always highest in the Two Main Arteries that leave the Heart.
5. Blood Pressure is maintain by TWO WAYS:  (1)  The Nervous System, which can speed up or slow down the Heart Rate; (2)  The KIDNEYS, which regulate blood pressure by the amount of fluid in our Blood.
6. When our pressure is too high, kidneys remove water from blood, lowering the total amount of fluid in the Circulatory System.
7. Both High and LOW Blood Pressure can cause our bodies problems.
8.  Blood Pressure is Usually Measured in the Artery Supplying the upper Arm.
9. To measure Blood Pressure:
  A. A Cuff is inflated around a persons arm - stopping the flow of blood through the artery.
    B. Air Pressure in the Cuff is slowly released- the first sounds of blood passing through the artery means that the Ventricles have pump with enough force to overcome the pressure exerted by the cuff.
    C. This measurement is known as the SYSTOLIC PRESSURE, or the pressure of the blood when it leaves the Ventricles.  NORMAL PRESSURE IS ABOUT 120 mm Hg FOR MALES, AND 110 mm Hg FOR FEMALES.
    D. Air pressure is continued to be released - listening for the disappearance of Sound, which indicates a steady flow of blood.  This known as the DIASTOLIC PRESSURE, or the pressure of the blood is sufficient to keep arteries open constantly even with the Ventricles Relax.  NORMAL PRESSURE IS ABOUT 80 mm Hg FOR MALES AND 70 mm Hg FOR FEMALES.
    E. YOUR BLOOD PRESSURE IS GIVEN TO AS THE SYSTOLIC NUMBER OVER THE DIASTOLIC NUMBER.
THE LYMPHATIC SYSTEM
1. As Blood Circulates throughout the body, Fluid from the Blood LEAKS into tissue.
2. A NETWORK OF VESSELS KNOWN AS THE LYMPHATIC SYSTEM COLLECTS THE FLUID AND RETURNS IT TO THE CIRCULATORY SYSTEM. (Figure 47-10)
3. The loss Fluid is known as LYMPH, a transparent yellowish fluid, and is collected in Lymphatic Capillaries and moves to larger Lymph Vessels.  Like Veins Lymph Vessels contain valves to prevent the back flow of lymph. Lymph vessels form a one-way system that returns fluids collected in tissues back to the bloodstream.
4.  The Lymphatic system has no pump like the heart, lymph must be moved through vessels by the squeezing of skeletal muscles.
5. These Lymph Vessels Pass Through small bean-shaped enlargements (organs) called LYMPH NODES, WHICH ACTS AS FILTERS AND PRODUCERS OF SPECIAL WHITE BLOOD CELLS CALLED LYMPHOCYTES THAT ARE SPECIALIZED TO FIGHT INFECTION.
6. The Fluid is returned to the Circulatory System at an opening in a Vein located under the Left Clavicle, or Collarbone, just below the shoulder.
 
 
SECTION 47-2 BLOOD
Blood is a Liquid Connective Tissue that constitutes the transport medium of the circulatory system.  The Two main functions of blood are to transport nutrients and oxygen to the cells and carry carbon dioxide and waste materials away from the cells.   Blood also transfers heat to the body surface and plays a role in defending the body against disease.
OBJECTIVES:  List the components of blood. Distinguish between red blood cells, white blood cells, and platelets in terms of structure and function.  Summarize the process of blood clotting.  Explain what determine the compatibility of blood types for transfusion.
1. The Main Function of the Circulatory System is to Transport Material in a FLUID Medium throughout the body.
2. THIS FLUID MEDIUM IS CALLED BLOOD.  BLOOD IS A TYPE OF LIQUID CONNECTIVE TISSUE THAT HAS MANY FUNCTIONS. Blood is composed of a Liquid Medium and Blood Solids.  The liquid makes up about 55 percent of the blood, and blood solids make up the remaining 45 percent.
3. BLOOD TRANSPORT NUTRIENTS, DISSOLVED GASES (O2, CO2), ENZYMES, HORMONES, AND WASTE PRODUCTS.
4. BLOOD REGULATES BODY TEMPERATURE, pH, and ELECTROLYTES.
5. BLOOD PROTECTS THE BODY FROM INVADERS, AND BLOOD RESTRICTS THE LOSS OF FLUID.
6. Our Bodies contains 4 to 5 liters of Blood.
BLOOD PLASMA
1. Approximately 55 percent of Blood in made up of a Fluid Portion called PLASMA.
2. Plasma is the Straw-Colored Liquid portion of Blood and is 90 Percent Water and 10 percent dissolved fats, salts, sugars, and Proteins called PLASMA PROTEINS.
3. THE PLASMA PROTEINS ARE DIVIDED INTO THREE TYPES:
    A.  ALBUMINS - HELP REGULATE OSMOTIC PRESSURE (MAINTAIN NORMAL BLOOD VOLUME AND BLOOD PRESSURE). THIS IS THE MOST ABUNDANT PLASMA PROTEIN.
    B.  GLOBULINS OR ANTIBODIES - INCLUDE ANTIBODIES THAT HELP FIGHT OFF INFECTION.  ANTIBODIES INITIATE THE DESTRUCTION OF PATHOGENS AND PROVIDE US WITH IMMUNITY.
    C.  FIBRINOGEN - RESPONSIBLE FOR THE ABILITY OF BLOOD TO CLOT.
BLOOD CELLS OR SOLIDS
THE CELLULAR PORTION OF BLOOD MAKE UP THE OTHER 45 PERCENT AND  INCLUDES SEVERAL TYPES OF HIGHLY SPECIALIZED CELLS AND CELL FRAGMENTS.  THEY ARE RED BLOOD CELLS (RBC), WHITE BLOOD CELLS (WBC), AND PLATELETS.
RED BLOOD CELLS (RBC) ERYTHROCYTES
1. RBC are the most numerous of the Blood Cells. One microliter of blood contains approx. 5 million RBCs.  (Figure 47-11)
2. RBC are BICONCAVE, or shaped so that they are narrower in the center than along the edges.
3. RBC are produced from cells in the Bone Marrow, they are gradually filled with HEMOGLOBIN which forces out the nucleus and other organelles.
4. Mature RBC do not have a Cell Nucleus and Organelles.  The Mature RBC becomes little more than a membrane sac containing Hemoglobin.
5. Hemoglobin is the iron-containing protein that gives RBC the ability to carry Oxygen.  Hemoglobin gives the RBC their color.
6. RBC stay in circulation for about 120 days before they are destroyed by special WBC in the liver and spleen.  RBC in your body are dying and being replace at a rate of about 2 million per second.
WHITE BLOOD CELLS (WBC) LEUKOCYTES
1. Outnumbered by RBC almost 500 to 1.
2. WBC are produced in the Red Bone Marrow, The Lymph Nodes, and the Spleen.  They are larger than RBC, almost Colorless, and do NOT Contain Hemoglobin. (Figure 47-12)
3. WBC have a Nucleus and can live for many months or years.
4. THE MAIN FUNCTION OF WBC IS TO PROTECT THE BODY AGAINST INVASION BY FOREIGN CELLS OR SUBSTANCES.
5. WBC called PHAGOCYTES can destroy bacteria and foreign cells by Phagocytosis (engulfed and digested), some produce special proteins called ANTIBODIES, and some release special chemicals that help the body fight off disease and resist infection.
6. Doctors are able to detect the presence of infection by counting the number of WBC in the blood.  When a person has an infection, the number of WBC can Double.
PLATELETS AND BLOOD CLOTTING
1. Platelets are NOT Cells; they are tiny Fragments of other Cells that were formed in the bone marrow.
2. Platelets are formed when small pieces of Cytoplasm are pinched off the large cells in the Red Bone Marrow called MEGAKARYOCYTES, which are found in the Bone Marrow.  Platelets lack a nucleus and their life span is about 7 to 11 days.
3. Platelets play an important role in Blood Clotting.
4. Platelets help the Clotting process by Clumping together and forming a Plug at the site of a wound and then releasing proteins called CLOTTING FACTORS.
5. Clotting Factors start a series of Chemical Reactions that ends with a sticky meshwork of Fibrin Filaments that stop bleeding by producing a clot. (Figure 47-14)
6. A genetic disorder of Clotting Factors is called HEMOPHILIA, suffers may bleed uncontrollably from even a small cut or scrape.
7. Clotting of blood in Vessels can block the flow of blood, if this happens in the brain, brain cells may die, causing a STROKE.
BLOOD TYPES
1. Blood type is determined by the Type of ANTIGEN present on the Surface of RBC.
2. An ANTIGEN is a protein or carbohydrate that acts as a signal, enabling the body to recognize foreign substances in the body.
3. Blood from Humans is Classified into FOUR GROUPS, based on the Antigens on the Surface of RBC. (Table 47-1)
4. BLOOD TYPING involves identifying the Antigens in a Sample.
5. THREE of the most important human antigens are called A, B, and Rh.
6. The A-B-O System is based on the A and B Antigen. It is a means of classifying blood by the Antigens located on the surface of RBC and the Antibodies circulating in the Plasma.
7. An Individual's RBC may carry an A ANTIGEN, a B ANTIGEN, both A and B ANTIGENS, OR NO ANTIGEN AT ALL. These Antigen patterns are called BLOOD TYPES A, B, AB, O RESPECTIVELY.   (Table 47-1)
8. Type AB is known as a Universal Receiver, meaning that they can receive any type blood.
9. Type O is known as a Universal Donor, meaning they can donate blood to anyone.
 
Rh SYSTEM
1. An antigen that is sometimes on the surface of RBC is the Rh FACTOR, named after the rhesus monkey in which it was first discovered.
2. Eighty-five percent of the U.S. population is Rh-positive (Rh+), meaning that Rh Antigens are present.
3. People who do not have Rh Antigens are called Rh-negative (Rh-).
4. If an Rh- person receives a transfusion of blood that has Rh+ antigens, Rh- antibodies will react with the Antigen and Agglutination (clumping) will occur.
5. The Rh Factor is the reason there are blood test before marriage.  The most serious problem with Rh incompatibility occurs during pregnancy.
6. If the mother is Rh- and the father is Rh+, the child may inherit the Dominant Rh+ allele (gene) from the father.
7. If the babies Rh+ blood gets into the mother during delivery, the mother will develop Antibodies to the Rh Factor.
8. If a second Rh+ child is conceived later, the mother's antibodies can cross the placenta and attack the blood of the fetus.
9. This condition is called ERYTHROBLASTOSIS FETALIS.
10.  To prevent this condition, an Rh- mother of an Rh+ child can by given Antibodies to destroy and Rh+ cells that have entered her bloodstream from the fetus.
11. The antibodies, a substance called RHOGAM, must be administered to the mother within Three Days after the birth of her first Rh+ child to remove from her bloodstream any Rh+ antibodies.
12.  By destroying any Rh+ cells in her bloodstream, any danger to a second child is prevented because the mother will not make any Antibodies against the blood cells of the Rh+ fetus.
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