Anatomy Cva

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ANATOMY AND PHYSIOLOGY

The Cardiovascular System

The heart and circulatory system make up the cardiovascular system. The heart works

as a pump that pushes blood to the organs, tissues, and cells of the body. Blood delivers oxygen

and nutrients to every cell and removes the carbon dioxide and waste products made by those

cells. Blood is carried from the heart to the rest of the body through a complex network of

arteries, arterioles, and capillaries. Blood is returned to the heart through venules and veins.

The one-way circulatory system carries blood to all parts of the body. This process of

blood flow within the body is called circulation. Arteries carry oxygen-rich blood away from the

heart, and veins carry oxygen-poor blood back to the heart. In pulmonary circulation, though,

the roles are switched. It is the pulmonary artery that brings oxygen-poor blood into the lungs

and the pulmonary vein that brings oxygen-rich blood back to the heart. (Rod R. Seeley et. al,

Essentials of Anatomy and Physiology 5th edition, McGraw-Hill Int. NY 10020 2005)

Twenty major arteries make a path through the tissues, where they branch into smaller

vessels called arterioles. Arterioles further branch into capillaries, the true deliverers of oxygen

and nutrients to the cells. Most capillaries are thinner than a hair. In fact, many are so tiny, only

one blood cell can move through them at a time. Once the capillaries deliver oxygen and

nutrients and pick up carbon dioxide and other waste, they move the blood back through wider

vessels called venules. Venules eventually join to form veins, which deliver the blood back to

the heart to pick up oxygen. Vasoconstriction or the spasm of smooth muscles around the

blood vessels causes and decrease in blood flow but an increase in pressure. In vasodilation, the

lumen of the blood vessel increase in diameter thereby allowing increase in blood flow. There is

no tension on the walls of the vessels therefore, there is lower pressure. (Rod R. Seeley et. al,

Essentials of Anatomy and Physiology 5th edition, McGraw-Hill Int. NY 10020 2005)

Various external factors also cause changes in blood pressure and pulse rate. An

elevation or decline may be detrimental to health. Changes may also be caused or aggravated

by other disease conditions existing in other parts of the body. The blood is part of the

circulatory system. Whole blood contains three types of blood cells, including: red blood cells,

white blood cells and platelets.



Blood also contains important proteins called clotting factors, which are critical to the

clotting process. Although platelets alone can plug small blood vessel leaks and temporarily

stop or slow bleeding, the action of clotting factors is needed to produce a strong, stable clot.

Platelets and clotting factors work together to form solid lumps to seal leaks, wounds,

cuts, and scratches and to prevent bleeding inside and on the surfaces of our bodies. The

process of clotting is like a puzzle with interlocking parts. When the last part is in place, the clot

is formed.

When large blood vessels are cut the body may not be able to repair itself through

clotting alone. In these cases, dressings or stitches are used to help control bleeding.

In addition to the cells and clotting factors, blood contains other important substances,

such as nutrients from the food that has been processed by the digestive system. Blood also

carries hormones released by the endocrine glands and carries them to the body parts that

need them. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-Hill

Int. NY 10020 2005)

Blood is essential for good health because the body depends on a steady supply of fuel

and oxygen to reach its billions of cells. Even the heart couldn't survive without blood flowing

through the vessels that bring nourishment to its muscular walls. Blood also carries carbon

dioxide and other waste materials to the lungs, kidneys, and digestive system, from where they

are removed from the body. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th

edition, McGraw-Hill Int. NY 10020 2005)

The Nervous System

The Nervous system is a network of specialized cells that communicate information

about an animals surroundings and its self, it processes this information and causes reactions in

other parts of the body. It is composed of neurons and other specialized cells called glia, that

aid in the function of the neurons.

The nervous system is divided broadly into two categories; the peripheral nervous

system and the central nervous system. Neurons generate and conduct impulses between and

within the two systems. The peripheral nervous system is composed of sensory neurons and

the neurons that connect them to the nerve cord, spinal cord and brain, which make up the

central nervous system. In response to stimuli, sensory neurons generate and propagate signals

to the central nervous system which then process and conduct back signals to the muscles and



glands. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-Hill Int.

NY 10020 2005)

The neurons of the nervous systems of animals are interconnected in complex

arrangements and use electrochemical signals and neurotransmitters to transmit impulses from

one neuron to the next. The interaction of the different neurons form neural circuits that

regulate an organisms perception of the world and what is going on with its body, thus

regulating its behavior. Nervous systems are found in many multicellular animals but differ

greatly in complexity between species.

The central nervous system (CNS) is the largest part of the nervous system, and includes

the brain and spinal cord. The spinal cavity holds and protects the spinal cord, while the head

contains and protects the brain. The CNS is covered by the meninges, a three layered protective

coat. The brain is also protected by the skull, and the spinal cord is also protected by the

vertebrae. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-Hill

Int. NY 10020 2005)

Brain is a part of the Central Nervous System, it plays a central role in the control of

most bodily functions, including awareness, movements, sensations, thoughts, speech, and

memory. Some reflex movements can occur via spinal cord pathways without the participation

of brain structures. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition,

McGraw-Hill Int. NY 10020 2005)

The cerebrum is the largest part of the brain and controls voluntary actions, speech,

senses, thought, and memory. The surface of the cerebral cortex has grooves or infoldings

(called sulci), the largest of which are termed fissures. Some fissures separate lobes. The

convolutions of the cortex give it a wormy appearance. Each convolution is delimited by two

sulci and is also called a gyrus (gyri in plural). The cerebrum is divided into two halves, known as

the right and left hemispheres. A mass of fibers called the corpus callosum links the

hemispheres. The right hemisphere controls voluntary limb movements on the left side of the

body, and the left hemisphere controls voluntary limb movements on the right side of the body.

Almost every person has one dominant hemisphere. Each hemisphere is divided into four lobes,

or areas, which are interconnected.



The frontal lobes are located in the front of

the brain and are responsible for voluntary

movement and, via their connections with

other lobes, participate in the execution of

sequential tasks; speech output;

organizational skills; and certain aspects of

behavior, mood, and memory.

The parietal lobes are located behind the

frontal lobes and in front of the occipital lobes. They process sensory information such as

temperature, pain, taste, and touch. In addition, the processing includes information about

numbers, attentiveness to the position of ones body parts, the space around ones body, and

one's relationship to this space.

The temporal lobes are located on each side of the brain. They process memory

and auditory (hearing) information and speech and language functions.

The occipital lobes are located at the back of the brain. They receive and process visualinformation (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-

Hill Int. NY 10020 2005)

Cranial nerve I: Olfactory nerve

The olfactory nerve is composed of axons from the olfactoryreceptors in the nasal sensory epithelium. It carries olfactory

information (sense of smell) to the olfactory bulb of the brain. This

is a pure sensory nerve fiber.

Cranial nerve II: Optic nerve

The optic nerve is composed of axons of the ganglion cells in theeye. It carries visual information to the brain. This is a pure sensory

nerve fiber. This nerve travels posteromedially from the eye,

exiting the orbit at the optic canal in the lesser wing of the

sphenoid bone. The optic nerves join each other in the middle

cranial fossa to form the optic chiasm.



Cranial nerve III: Oculomotor nerve

The oculomotor nerve is composed of motor axons coming from

the oculomotor nucleus and the edinger-westphal nucleus in the

rostral midbrain located at the superior colliculus level. This is a

pure motor nerve. It provides somatic motor innervation to four of the extrinsic eye muscles: the superior rectus, inferior rectus,

medial rectus, and the inferior oblique muscles. It also innervates

the muscles of the upper eyelid and the intrinsic eye muscles (the

pupillary eye muscle.) Together, CN III, CN IV and CN VI control the six muscles of the eye.

Cranial nerve IV: Trochlear nerve

The trochlear nerve provides somatic motor innervation to the superior oblique eye muscle.

This cranial nerve originates at the trochlear nucleus located in the tegmentum of the midbrain

at the inferior colliculus level and exits the posterior side of the brainstem. It is also a pure

motor nerve fiber.

Cranial nerve V: Trigeminal nerve

The trigeminal is the largest cranial nerve . It provides sensory

information from the face, forehead, nasal cavity, tongue, gums

and teeth (touch, and temperature) and provides somatic motorinnervation to the muscles of mastication or chewing.

This cranial nerve has 3 branches: the ophthalmic, maxillary and

mandibular branches.

It is composed of both sensory and motor axons. The sensory fibers are located in the

trigeminal ganglion and the motor fibers project from nuclei in the pons.

Cranial nerve VI: Abducens nerve

The abducens nerve carries somatic motor innervation to one of

the extrinsic eye muscles, the lateral rectus muscle. It is another pure

motor nerve fiber and originates from the abducens nucleus located in

the caudal pons at the facial colliculus level.

Cranial nerve VII: Facial nerve

The facial nerve carries somatic motor innervation to the many

muscles for facial expression. It carries sensory information form

the face (deep pressure sensation) and taste information from the

anterior two thirds of the tongue. It arises at the pons in thebrainstem and it emerges through openings in the temporal bone

and stylomastoid foramen and has many branches. It is composed

of both sensory and motor axons.



Cranial nerve VIII: Vestibulocochlear nerve

The vestibulocochlear nerve innervates the hair cell receptors of the

inner ear. It carries vestibular information to the brain from the

semicircular canals, utricle, and saccule providing the sense of

balance. It also carries information from the cochlea providing thesense of hearing. This cranial nerve branches into the Vestibular

branch (balance) and the cochlear branch (hearing). The cochlear

fibers originate from the spiral ganglion. It is pure sensory nerve

fiber.

Cranial nerve IX: Glossopharyngeal nerve

The glossopharyngeal nerve innervates the pharynx (upper part of

the throat), the soft palate and the posterior one-third of the

tongue. It carries sensory information (touch, temperature, and

pressure) from the pharynx and soft palate. It carries taste

sensation from the taste buds on the posterior one third of the

tongue. It provides somatic motor innervation to the throat muscles

involved in swallowing. It provides visceral motor innervation to the

salivary glands. This cranial nerve also supplies the carotid sinus and

reflex control to the heart . It is composed of both sensory and

motor axons and originates from the nucleus ambiguous in thereticular formation of the medulla.

Cranial nerve X: Vagus nerve

The vagus nerve consists of many rootlets that come off of the

brainstem just behind the glossopharyngeal nerve. The branchial

motor component originates from the nucleus ambiguous in the

reticular formation of the medulla. The visceral component

originates from the dorsal motor nucleus of the vagus located in the

floor of the fourth ventricle in the rostral medulla and in the central

grey matt er of the caudal medulla. It is the longest cranial nerve

innervating many structures in the throat, including the muscles of

the vocal cords, thorax and abdominal cavity. It provides sensory information (touch,

temperature and pressure) from the external auditory meatus (ear canal) and a portion of the

external ear. It carries taste sensation from taste buds in the pharynx. It also provides sensory

information from the esophagus, respiratory tract, and abdominal viscera (stomach, intestines,

liver, etc.). It provides visceral motor innervation to the heart, stomach, intestines, and

gallbladder. It is part of the ANS, the parasympathetic branch. It is composed of both sensory

and motor axons. Other parasympathetic ganglia include CN III , CN VII and CN IX .



Cranial nerve XI: Spinal Accessory nerve

The spinal accessory nerve has two branches. The cranial branch

provides somatic motor innervation to some of the muscles in the

throat involved in swallowing. This cranial branch is accessory to CN

X, originating in the caudal nucleus ambiguous, with the fibers of the cranial root traveling the same extracranial path as the

branchial motor component of the vagus nerve. The spinal branch

provides somatic motor innervation to the trapezius muscles,

providing muscle movement for the upper shoulders head and

neck. It is pure motor nerve fiber.

Cranial nerve XII: Hypoglossal nerve

The hypoglossal nerve provides somatic motor innervation to the muscles of the tongue. This

pure motor nerve originates from the hypoglossal nucleus located in the tegmentum of the

medulla.

Circle of Willis

The Circle of Willis (also called Willis' Circle, cerebral arterial circle, arterial Circle of

Willis, and Willis Polygon) is a circle of arteries that supply blood to

the brain.

Components

The Circle of Willis comprises the following arteries

y Anterior cerebral artery (left and right)

y Anterior communicating artery

y Internal carotid artery (left and right)

y Posterior cerebral artery (left and right)

y Posterior communicating artery (left and right)

The left and right internal carotid arteries arise from the right and left

common carotid arteries.

The posterior communicating artery is given off as a branch of the internal carotid artery just

before it divides into its terminal branches - the anterior and middle cerebral arteries. The anterior

cerebral artery forms the anterolateral portion of the Circle of Willis, while the middle cerebral

artery does not contribute to the circle.

The right and left posterior cerebral arteries arise from the basilar artery, which is formed by the

left and right vertebral arteries. The vertebral arteries arise from the subclavian arteries.

The anterior communicating artery connects the two anterior cerebral arteries and could be said to

arise from either the left or right side.

All arteries involved give off cortical and central branches. The central branches supply the interior

of the Circle of Willis, more specifically, the Interpeduncular fossa. The cortical branches are named



Like kidney beans, the bodys kidneys are dark red in color and have a shape in which

one side is convex, or rounded, and the other is concave, or indented. The kidneys of adult

humans are about 10 to 13 cm (4 to 5 in) long and about 5 to 7.5 cm (2 to 3 in) wideabout the

size of a computer mouse.

The kidneys lie against the rear wall of the abdomen, on either side of the spine. They

are situated below the middle of the back, beneath the liver on the right and the spleen on the

left. Each kidney is encased in a transparent, fibrous membrane called a renal capsule, which

helps protect it against trauma and infection. The concave part of the kidney attaches to two of

the bodys crucial blood vesselsthe renal artery and the renal veinand the ureter, a tubelike

structure that carries urine to the bladder. (Rod R. Seeley et. al, Essentials of Anatomy and

Physiology 5th edition, McGraw-Hill Int. NY 10020 2005)

A primary function of kidneys is the removal of poisonous wastes from the blood. Chief

among these wastes are the nitrogen-containing compounds urea and uric acid, which result

from the breakdown of proteins and nucleic acids. Life-threatening illnesses occur when too

many of these waste products accumulate in the bloodstream. Fortunately, a healthy kidney

can easily rid the body of these substances.

In addition to cleaning the blood, the kidneys perform several other essential functions.

One such activity is regulation of the amount of water contained in the blood. This process is

influenced by antidiuretic hormone (ADH), also called vasopressin, which is produced in the

hypothalamus (a part of the brain that regulates many internal functions) and stored in the

nearby pituitary gland. Receptors in the brain monitor the bloods water concentration. When

the amount of salt and other substances in the blood becomes too high, the pituitary gland

releases ADH into the bloodstream. When it enters the kidney, ADH makes the walls of the

renal tubules and collecting ducts more permeable to water, so that more water is reabsorbed

into the bloodstream. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition,


The hormone aldosterone, produced by the adrenal glands, interacts with the kidneys

to regulate the bloods sodium and potassium content. High amounts of aldosterone cause the

nephrons to reabsorb more sodium ions, more water, and fewer potassium ions; low levels of

aldosterone have the reverse effect. The kidneys responses to aldosterone help keep the

bloods salt levels within the narrow range that is best for crucial physiological activities. (Rod R.

Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-Hill Int. NY 10020

2005)



Aldosterone also helps regulate blood pressure. When blood pressure starts to fall, the

kidney releases an enzyme (a specialized protein) called renin, which converts a blood protein

into the hormone angiotensin. This hormone causes blood vessels to constrict, resulting in a

rise in blood pressure. Angiotensin then induces the adrenal glands to release aldosterone,

which promotes sodium and water to be reabsorbed, further increasing blood volume and

blood pressure.

The kidney also adjusts the body's acid-base balance to prevent such blood disorders as

acidosis and alkalosis, both of which impair the functioning of the central nervous system. If the

blood is too acidic, meaning that there is an excess of hydrogen ions, the kidney moves these

ions to the urine through the process of tubular secretion. An additional function of the kidney

is the processing of vitamin D; the kidney converts this vitamin to an active form that stimulates

bone development. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition,


Several hormones are produced in the kidney. One of these, erythropoietin, influences

the production of red blood cells in the bone marrow. When the kidney detects that the

number of red blood cells in the body is declining, it secretes erythropoietin. This hormone

travels in the bloodstream to the bone marrow, stimulating the production and release of more

red cells. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-Hill

Int. NY 10020 2005)

The Respiratory System

The respiratory system generally includes tubes, such as the

bronchi, used to carry air to the lungs, where gas exchange

takes place. A diaphragm pulls air in and pushes it out.

Respiratory systems of various types are found in a wide variety

of organisms. Even trees have respiratory systems.

In humans, the respiratory system consists of the

airways, the lungs, and the respiratory muscles that mediate the

movement of air into and out of the body. Within the alveolar

system of the lungs, molecules of oxygen and carbon dioxideare passively exchanged, by diffusion, between the gaseous

environment and the blood. Thus, the respiratory system facilitates oxygenation of the blood

with a concomitant removal of carbon dioxide and other gaseous metabolic wastes from the

circulation. The system also helps to maintain the acid-base balance of the body through the



efficient removal of carbon dioxide from the blood. (Rod R. Seeley et. al, Essentials of Anatomy

and Physiology 5th edition, McGraw-Hill Int. NY 10020 2005)

Mechanics of Breathing

To take a breath in, the external intercostal muscles contract, moving the ribcage up and

out. Thediaphragm moves down at the same time, creating negative pressure within the

thorax. The lungs are held to the thoracic wall by the pleural membranes, and so expand

outwards as well. This creates negative pressure within the lungs, and so air rushes in through

the upper and lower airways.

Expiration is mainly due to the natural elasticity of the lungs, which tend to collapse if

they are not held against the thoracic wall. This is the mechanism behind lung collapse if there

is air in the pleural space (pneumothorax). (Rod R. Seeley et. al, Essentials of Anatomy and

Physiology 5th edition, McGraw-Hill Int. NY 10020 2005)

Physiology of Gas Exchange

Each branch of the bronchial tree eventually sub-divides to form very narrow terminal

bronchioles, which terminate in the alveoli. There are many millions of alveoli in each lung, and

these are the areas responsible for gaseous exchange, presenting a massive surface area for

exchange to occur over.

Each alveolus is very closely associated with a network of capillaries containing

deoxygenated blood from the pulmonary artery. The capillary and alveolar walls are very thin,

allowing

rapid exchange of gases by passive diffusion along concentration gradients.

CO2 movesinto the alveolus as the concentration is much lower in the alveolus than in

the blood, and O2 moves out of the alveolus as the continuous flow of blood through the

capillaries prevents saturation of the blood with O2 and allows maximal transfer across the

membrane. (Rod R. Seeley et. al, Essentials of Anatomy and Physiology 5th edition, McGraw-Hill

Int. NY 10020 2005)

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