anatomy and physiology 3c group 2 cp

8/9/2019 Anatomy and Physiology 3c Group 2 Cp

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The endocrine system is one of the bodys

main systems for communicating,

controlling and coordinating the bodys

work. It works with the nervous system,

reproductive system, kidneys, gut, liver,

pancreas and fat to help maintain and

control the following:

body energy levels

reproduction growth and development

internal balance of body systems,

called homeostasis

responses to surroundings, stress

and injury

The endocrine system accomplishes these

tasks via a network of glands and organs

that produce, store, and secrete certain

types of hormones. Hormones are special

chemicals that move into body fluid after

they are made by one cell or a group of

cells. Different types of hormones cause

different effects on other cells or tissues of

the body.Endocrine glands make hormones that are used inside the body. Other glands make

substances like saliva, that reach the outside of the body. Endocrine glands and endocrine-related

organs are like factories. They produce and store hormones and release them as needed. When

the body needs these substances, the bloodstream carries the proper types of hormones to

specific targets. These targets may be organs, tissues, or cells. To function normally, the body


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needs glands that work correctly, a blood supply that works well to move hormones through the

body to their target points, receptor places on the target cells for the hormones to do their work,

and a system for controlling how hormones are produced and used.

Endocrine system diseases and disorders happen when one or more of the endocrine

systems in your body are not working well. Hormones may be released in amounts that are too

great or too small for the body to work normally. These irregularities are also called a hormone

imbalance. There may not be enough receptors, or binding sites, for the hormones so that they

can direct the work that needs to be done. These hormone imbalances may be the result of a

problem with the system regulating the hormones in the blood stream, or the body may have

difficulty controlling hormone levels because of problems clearing hormones from the blood. For

example, a hormone imbalance may occur if a person's liver or kidneys are not working well,

resulting in a hormone level in the bloodstream that is too high.


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The Pancreas is a fish-shapedspongy grayish-pink organ about 6 inches

(15 cm) long that stretches across the

back of the abdomen, behind the stomach.

The head of the pancreas is on the right

side of the abdomen and is connected to

the duodenum (the first section of the

small intestine). The narrow end of the

pancreas, called the tail, extends to the

left side of the body.

The pancreas makes pancreatic juices and hormones, including insulin. The pancreatic juices are

enzymes that help digest food in the small intestine. Insulin controls the amount of sugar in the

blood.

As pancreatic juices are made, they flow into the main pancreatic duct. This duct joins the

common bile duct, which connects the pancreas to the liver and the gallbladder. The common

bile duct, which carries bile (a fluid that helps digest fat), connects to the small intestine near the

stomach.

The pancreas is thus a compound gland. It is "compound" in the sense that it is composed of both

exocrine and endocrine tissues. The exocrine function of the pancreas involves the synthesis and

secretion of pancreatic juices. The endocrine function resides in the million or so cellular islands

(the islets of Langerhans) embedded between the exocrine units of the pancreas. Beta cells of the

islands secrete insulin, which helps control carbohydrate metabolism. Alpha cells of the islets

secrete glucagon that counters the action of insulin.
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Beta Cells & Insulin Production

Healthy beta cells are constantly making

insulin and storing it. Those same beta cells release

small amounts of insulin day & night, whether the

person's eaten or not. This is how the body distributes

its naturalbasal insulin. This is important to the body

because it is the basal insulin which allows cells to

use blood sugar.

When the insulin level drops, this signals the liver to release glucose by converting stored

carbohydrates (glycogen) into glucose for fuel. This release and conversion raises blood glucose

levels. It's the body's built in "fail-safe" mechanism to prevent hypoglycemia.

When this occurs, if there are not enough stored carbohydrates in the form of glycogen,

the liver will convert protein into glucose in an attempt to keep the body going. If there's not

enough carbohydrates or enough protein in the diet, the liver will begin turning body muscle into

glucose to keep itself alive.
http://petdiabetes.wikia.com/wiki/Basalhttp://petdiabetes.wikia.com/wiki/Hypoglycemiahttp://petdiabetes.wikia.com/wiki/Basalhttp://petdiabetes.wikia.com/wiki/Hypoglycemia


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Insulin

The actions of insulin are

threefold: (1) itpromotes glucose

uptake by target cells and

provides for glucose storage as

glycogen, (2) it prevents fat and

glycogen breakdown, inhibits

gluconeogenesis and (3) increase

protein synthesis. Insulin acts to

promote fat storage by increasing

the transport of glucose into fat

cells. It also facilitates

triglycerine synthesis from

glucose in fat cells and inhibits the intracellular breakdown of stored triglycerides. Insulin also

inhibits protein breakdown and increases protein synthesis by increasing the active transport of

amino acids into body cells. Insulin also inhibits gluconeogenesis, or the building of glucose

from new sources, mainly amino acids.

When there is glucose in the bloodstream it triggers the release of insulin. A rise in blood

pressure levels results in glucose uptake into pancreatic beta calla, facilitated by an insulin-

independent, glucose- transporting proteins, GLUT-2. Metabolism via glycolysis generates ATP,

resulting in increase in cytoplasmic ATP ratios. This inhibits the activity of the ATP- sensitive

potassium channel on the beta cell membrane, leading to membrane depolarization and the influx

of calcium through voltage- dependent calcium channels. The resultant increase in intracellular

calcium stimulates secretion of insulin, presumably from stored hormone within the beta cell

granules. This is the phase of immediate release of insulin. If the secretory stimulus persists, a

delayed and protracted response follows that involves active synthesis of insulin. Other agents,


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including intestinal hormones and certain amino acids (leucine and arginine), stimulate insulin

release but not synthesis.

Insulin Action and Insulin

Signaling Pathway

Its principal metabolic function is to

increase the rate of glucose transport into

certain cells in the body. These are the

striated muscle cells and to a lesser extent,

adipocytes, representing collectively about

two thirds of the entire body weight.Glucose uptake in other peripheral tissues,

most notably the brain, is insulin-

independent. In the muscle cells, glucose

is then either stored as glycogen or oxidized to generate ATP. In adipose tissue, glucose is

primarily stored as lipid. Besides promoting lipid synthesis, insulin also inhibits lipid degradation

in adipocytes. Similarly, insulin promotes amino acids uptake and protein synthesis, while

inhibiting protein degradation. Thus, the anabolic effects of insulin are attributable to increased

synthesis and reduced degradation of glycogen, lipids, and proteins. In addition, insulin has

several mitogenic functions, including initiation of DNA synthesis in certain cells and

stimulation of their growth and differentiation.

It is increasingly recognized that adipose tissue is not merely a passive storage depot for

fats, but can also operate as a functional endocrine organ, releasing hormones in response to

changes in metabolic status. A variety of proteins released into the systemic circulation by

adipose tissue have been identified and these are collectively termed adipokines. Dysregulation

of adipokine secretion may be one of the mechanisms by which insulin resistance is tied to

obesity. Several adipokines have been implicated in insulin resistance, including leptin,

adiponectum and reistin. Leptin acts on the central nervous system receptors and other sites to

reduce food intake and induce satiety; it is also an insulin-sensitizing adipokine.


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Glucagon

Glucagon is a hormone produced by the alpha cells of the pancreas. Its effect is the

opposite of insulin-- it causes the liver to release stored glucose into the blood, raising blood

glucose levels. This process is called glycogenolysis. Glycogenolysis is creation of extra blood

glucose (from breakdown ofglycogen) by the liver, in response to glucagon. Glucagon is the

main counterregulatory hormone to insulin.

Glucagon also increases the transport of amino acids in the liver and stimulates their conversion

into glucose, a process called gluconeogenesis. Gluconeogenesis is the production of new

glucose in the body from non-sugar sources, mainly proteins. It occurs mainly in the liver and

kidneys. Because liver stores are limited, gluconeogenesis is important in maintaining blood

glucose levels over time.
http://petdiabetes.wikia.com/wiki/Pancreashttp://petdiabetes.wikia.com/wiki/Insulinhttp://petdiabetes.wikia.com/wiki/Blood_glucose_levelhttp://petdiabetes.wikia.com/wiki/Blood_glucose_levelhttp://petdiabetes.wikia.com/wiki/Glycogenolysishttp://petdiabetes.wikia.com/wiki/Glucagonhttp://petdiabetes.wikia.com/wiki/Counterregulatory_hormoneshttp://petdiabetes.wikia.com/wiki/Insulinhttp://en.wikipedia.org/wiki/Gluconeogenesishttp://petdiabetes.wikia.com/wiki/Pancreashttp://petdiabetes.wikia.com/wiki/Insulinhttp://petdiabetes.wikia.com/wiki/Blood_glucose_levelhttp://petdiabetes.wikia.com/wiki/Blood_glucose_levelhttp://petdiabetes.wikia.com/wiki/Glycogenolysishttp://petdiabetes.wikia.com/wiki/Glucagonhttp://petdiabetes.wikia.com/wiki/Counterregulatory_hormoneshttp://petdiabetes.wikia.com/wiki/Insulinhttp://en.wikipedia.org/wiki/Gluconeogenesis


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The Urinary System performs the vital function of removing the organic waste products

generated by the cells throughout the body. It also functions to regulate blood volume and

pressure, regulating plasma concentrations ions, stabilize blood pH and conserving valuable

nutrients.

Through these activities it will help regulated to keep all blood composition within limits

in ensure optimum functioning.

Kidney

The kidneys are bean shaped, brownish red structure that lie outside the peritoneal cavity in the

back of the upper abdomen, one on each side of the vertebral column at the level of the 12 th thoracic and


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3rd lumbar vertebrae. Normally, the right kidney is lower

than the left presumably because of the position of the

liver. The kidney is about 10-12 cm long, 5-6 cm wide,

2.5 cm deep and weighs about 113-170 grams. The

kidney is well protected by ribs, muscles, Gerotas fascia,

perirenal fat and renal capsule.

The kidney consists of two distinct regions, the renal

parenchyma and the renal pelvis. The renal parenchyma

is divided into the cortex and medulla. The cortex contains the gromeruli, proximal and distal tubules, and

cortical collecting ducts and their adjacent peritubular capillaries. The medulla resembles comical

pyramids. The pyramids are situated with the base facing the concave surface of the kidney and the apex

facing the hilum, or pelvis. Each kidney contains approximately 8 to 18 pyramids. The pyramids drain

into 4 to 13 minor calices that, in turn, drain into 2 to 3 calices that open directly into the renal pelvis.

On the medial side of each kidney are the hilum, where the renal artery and nerves enter and

where the renal vein and ureter exit the kidney. The hilum opens into a cavity called renal sinus, which

contains blood vessels, part of the system for collecting urine and fat.

The renal artery divides into smaller and smaller vessels, eventually to form the gromerulus,

which is the capillary bed responsible for glomerular filtration. Blood leaves the glomerulus through the

efferent arteriole and flows bask to the inferior vena cava through a network of capillaries and veins.

Each kidney contains about one million nephrons, the functional unit of the kidney. Each kidney

is capable of providing adequate renal function if the opposite kidney is damaged or becomes

nonfunctional. The nephrons consist of a glomerulus containing afferent and efferent arterioles,

Bowmans capsule, proximal tubule, loop of Henle, distal tubule, and collecting ducts. Collecting ducts

converges into papillae, which empty into the minor calices, which drains into three major calices that

open directly into the renal pelvis.

Nephrons are structurally divided into two types: cortical and juxtamedullary. Cortical nephrons are

found in the cortex of the kidney, and juxtamedullary nephrons sit adjacent to the medulla. The

juxtamedullary nephrons are distinguished by their long loop of Henle and vasa recta, long capillary loops


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that dip into the medulla of the kidney. The nephron is responsible for the actual purification and filtration

of the blood.

Bowmans Capsule is the cup shaped

mouth of a nephron. It is formed by two

layers of epithelial cells with a space called

Bowmans space. Fluid, waste products,

and electrolytes that pass through the

porous glomerular capillaries and enter this

space constitute the glomerular filtrate,

which will be processed in the nephron to

form urine.

The glomerulus is composed of three

filtrating layer: the capillary endothelium,

the basement membrane, and the epithelium. The glomerular membrane normally allows filtration of fluid

and small molecules yet limits passage of larger molecules, such as blood cells and albumin and other

protein molecules.

The proximal convoluted tubule is the second part of the nephron but the first part of the renal

tubule. Their walls consist of one layer of epithelial cells. These cells have a brush border facing the

lumen of the tubule. Thousands of microvilli form the brush border and greatly increase it luminal surface

area. 60% of the filtrate will be reabsorbed in the proximal convoluted tubule in which 99% of water

including sodium, chloride and glucose are reabsorbed. Normally glucose is excreted in the urine in a

normal amount, however, when there is hyperglycemia, glucose is no longer excreted because it exceeds

the normal renal threshold for glucose which is only 220 mg/dL.

The loop of Henle is the segment of renal tubule just beyond the proximal tube. It consists of a

descending limb, a sharp turn and an ascending limb. A nephron with a loop of Henle that dips far into

the medulla is a called a juxtamedullary nephron. The length of the loop of Henle is important in the

production of highly concentrated or very dilute urine.

The distal tubule is a convoluted portion of the tubule beyond the loop of Henle. Additional

water and electrolytes are reabsorbed in the distal convoluted tubule.


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Thejuxtaglomerular apparatus is found at the point where the afferent arteriole brushes past the distal

convoluted tubule. This structure is important in maintaining the homeostasis of blood flow because its

reflexively secretes renin.

The collecting duct is a straight tubule joined by the distal tubules of several nephrons.

Collecting ducts join larger ducts, and all larger collecting ducts of one renal papilla into one of the small

calyces.

The ureters are narrow, muscular tubes, each 24 to 30 cm long, that originates at the lower

portion of the renal pelvis and terminate in the trigone of the bladder wall. In human anatomy, the ureters

are muscular ducts that propel urine from the kidneys to the urinary bladder.There are three narrowed

areas of each ureter: the ureterpelvic junction, the ureter segment near the sacroiliac sac junction, and the

uretervesical junction.

The angling of the uretovesicular junction is the primary means of providing antegrade, or

downward, movement of urine, also referred to as efflux of urine. This anglish prevent vesicoureteral

reflux or backflow of urine. During voiding, increased intravesicular pressure keeps the ureterovesicular

junction closed and keeps urine within the ureter. As soon as micturition is completed, intravesicalpressure returns to its normal low baseline value, allowing efflux of urine to continue. The lining of the

ureters is made up of transitional cell epithelium called urothelium. The movement of the urine from the

renal pelves through the ureter into the bladder is facilitated by peristatltic waves from the contraction of

smooth muscles in the ureter wall.
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The urinary bladder is a muscular, hollow sac located just

behind the pubic bone. The adult bladder has the capacity of about 300

to 600 ml of urine. The bladder is characterized by its central, hollow

area called the vesicle, which has two inlets (ureter) and one outlet

(urethrovesicular junction), which is surrounded by the bladder neck.

The wall of the bladder is composed of four layers. The outermost

layer is the adventitia, which is made up of connective tissue. Beneath

the adventitia is a smooth muscle layer known as detrusor and beneath it is the lamina proporia which

serves as an interface between the detrusor and the innermost layer, the urothelium, which contains a

membrane that is impermeable to water. The bladder neck contains bundles of involuntary smooth muscle

that form a portion of the urethral sphincter known as the internal sphincter. The portion of the sphinteric

mechanism that is voluntary control is the external unrinary sphincter at the anterior urethra, the segment

most distal from the bladder.

The urethra is a tube which connects the urinary bladderto the outside of the body. The

urethra has an excretory function in both sexes to pass urine to the outside, and also a

reproductive function in the male, as a passage forsemen. The urethra rises from the base of the

bladder: in the male, it passes through the penis; and in the female it opens just anterior to the

vagina. In the male the prostate gland, this lies just below the bladder neck which surrounds the

urethra posteriorly and laterally.

Kidney Site of Red Blood Cell production

Erythroblasts arise from the primitive myeloid stem cells in the bone marrow. The

erythroblast is a nucleated cell that, in the process of maturing within the bone marrow,

accumulates hemoglobin and gradually loses its nucleus. As this stage, the cell is known as a

reticulocyte. Further maturation into an RBC entails the loss of the dark staining material and

slight shrinkage. The mature RBC is then released into the circulation.

Differentiation of the primitive myeloid stem cell of the marrow into an erythroblast is

stimulated by erythropoietin or dihydrocholecalciferol, a hormone produced primarily by the
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kidneys. If the kidney detects low levels of oxygen (that would occur in anemia) the release of

erythropoietin is increased. Its increase will stimulate the bone marrow to increase the production

RBCs.

Function of the Kidney in Relation to Calcium, Phosphorous, and Vitamin D Regulation

Although vitamin D functions as a vitamin, it is also classified as a hormone. It acts to

sustain normal serum levels of calcium and phosphate by increasing their absorption from the

intestine, and it also is necessary for normal bone formation. Vitamin D is a prohormone thatlack biological activity and must undergo metabolic transformation to achieve potency. Once

vitamin d enters the circulation from the skin or intestine, it is concentrated in the liver. There it

is hydroxylated to form 25- hydroxyvitamin D. it is transported to the kidney where it is

transformed into active 1,25-(OH)2D3. The major action of activated form of Vitamin D, is also

called carcitriol, is to increase absorption of calcium from the intestine. It also increases

intestinal reabsorption of calcium and sensitizes bone to the resorptive actions of parathyroid

hormone. The formation of 1,25-(OH)2D3 in the kidneys is regulated in feedback fashion by

serum calcium and phosphate levels. Low calcium levels lead to an increase parathyroid

hormone, which then increases vitamin D activation. A lowering serum phosphate also augments

vitamin D activation.

Physiology of Urine Formation

Transport process

Osmolality refers to the concentration of solution determined by the number of dissolves particles

per kilogram of water. The osmolality of intracellular fluid and extra cellular fluid tends to equalize

because of constant shifting of water.

Water and solutes are transported between membranes by the following processes:


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a. Diffusion is the random movement of particles in all directions. The natural tendency is for a

substance to move from a higher to a lower concentration. Facilitated diffusion is used when a carrier

protein transports the molecules through membranes of lower to higher concentration.

b. Active transport is when carrier proteins can transport substances from an area of lower

concentration to an area of equal or greater concentration. This process requires energy.

c. Filtration is the transfer of water solutes through a membrane from an area of greater pressure

to an area of low pr4essure. Filtration is necessary for moving fluids out of capillaries into the tissues and

for filtering plasma through the kidneys.

d. Osmosis is the movement of water across a membrane from less concentrated solution to a

more concentrated solution.

The Three Basic Process in Urine Formation

Filtration

An average of 21% of the blood pumped by the heart each minute flows through the kidneys. Of

the total volume of blood plasma that flows through the glomerular capillaries, about 19% passes through

the filtration membrane into Bowmans capsule to become filtrate. In all of the nephrons of both kidneys,

about 180 L of filtrate is produced each day, but only 1% or less of the filtrate becomes urine because

most of the filtrate is reabsorbed.

The filtration membrane allows some substances, but not others, to pass from the blood into

Bowmans capsule. Water and solutes of small size readily pass through the opening of the filtration

membrane but blood cells and proteins, which are too large to pass through the filtration membrane, do

not enter Bowmans capsule.

Reabsorption

As the filtrate flows from the Bowmans capsule through the proximal tubule, loop of Henle,

distal tubule, and collecting ducts, many of the solutes in the filtrate are reabsorbed. About 99% of the

original filtrate volume is reabsorbed and enters the peritubular capillaries. The reabsorbed filtrate flows

through the renal veins to enter the general circulation. Only 1% of the original filtrate volume becomes


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urine. Because excess ion and metabolic waste products are not readily reabsorbed, the small volume of

urine produced contains a high concentration of ions and metabolic waste products.

The proximal tubule is the primary site for the reabsorption of solutes and water. The cuboidal

cells of the proximal tubule have numerous microvilli and mitochondria, and they are well adapted to

transport molecules and ions across the wall of the nephron by active transport and cotransport.

Substances transported from the proximal tubule include proteins, amino acids, glucose, fructose

molecules as well as sodium, potassium and calcium. The proximal tubule is permeable to water. As

solute molecules are transported out of the proximal tubule into the interstial fluid, water moves by

osmosis in the same direction. The solutes and water then enter the peritubular capillaries. About 65% of

the filtrate volume is reabsorbed from the proximal tubule.

The descending limb of the loop of Henle functions to further concentrate the filtrate. The renal

medulla contains very concentrated interstitial fluid that has large amounts of sodium, chlorine and urea.

The wall of the thin segment of the descending limb is permeable to water and moderately permeable to

solutes. As the filtrate passes through the descending limb of the loop of Henle into the medulla of the

kidney, water moves out of the nephrons by osmosis, and some solutes move into the nephron by

diffusion. By the time the filtrate has passed through the descending limb, another 15% of the filtrate

volume has been reabsorbed, and the filtrate is as concentrated as the interstitial fluid of the medulla. The

reabsorbed filtrate enters the vasa recta.

The ascending loop of Henle functions to dilute filtrate by removing solutes. The thin segment of

the ascending limb is not permeable to water, but is permeable to solutes. Consequently solutes diffuse

out of the nephron.

The cuboidal epithelial cells of the thick segment of the ascending limb actively transport sodium

out of the nephron, and the potassium and chloride are contransported with sodium. The thick segment of

the ascending limb is not permeable to water. As a result, sodium, potassium and chloride, but little water

is removed from the filtrate. As a result, the diluted filtrate that enters the ascending limb becomes a

diluted solution by the time it reaches the distal tubule. As the filtrate enters the distal tubule, it is more

dilute than the interstitial fluid of the renal cortex. Also, because of the volume of filtrate reabsorbed in

the proximal tubule and the descending limb of Henles loop, only about 20% of the original filtrate

volume remains. The solutes transported from the ascending limb of the loop of Henle enter the

interstitial fluid of the medulla and help keep the concentration of solutes in the medulla high. Excess

solutes enter the vasa recta.


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The cuboidal cells of the distal

tubule and collecting duct function to

remove water and additional solutes.

Sodium and chlorine are reabsorbed.

Sodium ions are actively transported and

chlorine is contransported. Also, 19% of

the original filtrate volume is reabsorbed

by osmosis, leaving 1% of the original

filtrate as urine. The reabsorbed water

and solutes from the distal tubule enter

the peritubular capillaries and enter the

vasa recta form the collecting ducts.

Secretion

Secretion is the process by which substances move into the distal and collecting tubules from blood in the

capillaries around these tubules. In this respect, secretion is reabsorption in reverse. Whereas reabsorption

moves substances out of the tubules and into the blood, secretion moves substances out of the blood and

into the tubules where they mix with the water and other wastes and are converted into urine. These

substances are secreted through either an active transport mechanism or as a result ofdiffusion across

the membrane.

Substances secreted are hydrogen ions (H+), potassium ions (K+), ammonia (NH3), and certain drugs.

Kidney tubule secretion plays a crucial role in maintaining the body's acid-base balance, another example

of an important body function that the kidney participates in.

anatomy and physiology 3c group 2 cp

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