excretory and digestive system Flashcards
liver function
chemically modifies wastes and releases them into bile, deals with waste that can’t be filtered out by the kidneys,
synthesizes urea
colon function
reabsorbs water and ions from feces
kidney function
functions as a filtration system that removes unwanted materials from the blood and passes them to the bladder for storage and eventual elimination
- excretion of hydrophilic waste
- maintenance of constance solute concentration and constant pH
- maintenance of constant fluid volume (important for blood pressure and cardiac output)
Accomplished by filtration, selective reabsorption, and secretion, ultimately resulting in urine
renal artery
where blood enters the kidney
internal/external sphincter
control release of bladder
nephron
functional unit of the kidney
urine direction in kidney
empties from collecting ducts
direction of blood in filtration
renal artery to afferent arteriole to glomerulus to efferent arteriole.
Fluid then passes through filter (glomerular basement membrane) and enters Bowman’s capsule.
selective reabsorption
returning of some substances to the blood stream, usually via active transport.
They are then picked up by peritubular capillaries, which drain into venues that lead to the renal vein.
secretion
movement of substances into the filtrate, increasing the rate at which they are removed from the plasma
ADH function
prevents water loss in urine, increases water reabsorption in distal nephron (primarily the collecting duct), making it permeable to water.
Increases blood pressure
parts of nephron
capsule and renal tubule, which empties filtrate into a collecting duct
aldosterone function
released by adrenal cortex when blood pressure is low, causes increased reabsorption of Na+ by the distal nephron, causing increased thirst and water retention .
loop of Henle
where PCT empties into, has a long loop that dips into renal medulla.
Consists of a thin descending limb, which heads into the medulla, and an (part thin, part thick) ascending limb, which heads back out toward the cortex
different permeabilities of loop of Henle
descending limb is permeable to water, ascending limb is only permeable to ions,
This results in the loop of Henle being a countercurrent multiplier that creates a salty medulla facilitating water resorption from the collecting duct
distal/ proximal tubules
function in reabsorption
JG cells
found in afferent arteriole, monitors systemic blood pressure and secretes renin when a decrease In BP occurs. This catalyzes formation angiotensin II, which functions as a vasoconstrictor and raises blood pressure.
Glomerular filtration rate and pressure
correlated
How does kidney maintain constant blood pH
when plasma pH is too high, HCO3- is excreted in urine and when plasma pH is too low, H+ is excreted.
erythropoietin
made by kidneys, causes increases synthesis of red blood cells in the bone marrow
gastrointestinal tract
accomplishes digestion, long muscular tube extending from the mouth to the anus
GI lumen
inside of the gut, continuous with the space outside the body, innermost lining is composed of epithelial cells, which are responsible for most of the secretory activity of the GI tract
GI motility
rhythmic contraction of GI smooth muscle, serves the purpose of mixing food and moving food down the gut
peristalsis
orderly form of contraction responsible for movement of food down the GI tract
enteric nervous system
branch of ANS that helps to control digestion via innervation of the gastrointestinal tract, pancreas, and gall bladder
made up of two networks of neurons: myenteric plexus, which primarily helps to regulate gut motility and submucosal plexus, which is found in the submucosa and helps to regulate enzyme secretion, gut blood flow, and ion/water balance in the lumen
GI secretions
stimulated by food in the gut and by the parasympathetic nervous system, inhibited by sympathetic stimulation.
two types: exocrine (composed of specialized epithelial cells organized into sacs called acini) and endocrine, which empty into nearby capillaries.
gastric glands
found in stomach, secrete acid and pepsinogen.
goblet cells
found along entire GI tract, secrete mucus.
mouth function in digestion
fragmentation, lubrication, some enzymatic digestion
salivary amylase
found in saliva, hydrolyzes starch, breaking it into fragments.
pharynx
contains opening to trachea, which conveys air to and from the lungs and the esophagus, conveys food and drink to the stomach
stomach function
partial digestion of food, regulated release of food into small intestine, destruction of microorganisms
what causes conversion of pepsinogen to pepsin
acidity
pepsin
secreted by chief cells, catalyzes proteolysis
effect of pyloric sphincter contracting
inhibition of further stomach emptying, preventing passage of food from stomach into the duodenum
gastrin
hormone secreted by G cells when food is in the stomach, stimulates acid and pepsin secretion and gastric motility
small intestine
where food leaving the stomach enters, divided into the duodenum, jejunum, and ileum
villus
projection of the wall of the gut into the lumen, has three important structures:
- capillaries that absorb dietary monosaccharides and amino acids
- lacteals, capillaries which absorb dietary fats
- Peyer’s patches, which function as part of the immune system
two ducts that empty into the duodenum
pancreatic duct, which delivers the exocrine secretions of the pancreas, and the common bile duct which delivers bile.
function of bile
vehicle for disposal of waste products by the liver, essential for the digestion of fats
duodenal enzymes
enterokinase and brush border enzymes, which hydrolyze the smallest carbohydrates and proteins
three main duodenal hormones
CCK- secreted in response to fats in the duodenum, stimulating gallbladder contraction (bile release) and decreasing gastric motility
secretin - released in response to acid in the duodenum, causing pancreas to release large amounts of a high-pH aqueous buffer, neutralizing HCl released by the stomach enterogastrone - decreases stomach emptying
jejunum and ileum
where substances are absorbed if not absorbed in duodenum
colon
large intestine, role is to absorb water and minerals, and to form and store feces until time of defecation
colonic bacteria function
presence of large numbers of normal bacteria keeps dangerous bacteria from proliferating and they supply us with vitamin K
GI accessory organs
pancreas, liver, gallbladder, and salivary gland
function of pancreatic enzymes
released into duodenum and essential for digestion
how does nervous system affect pancreatic secretion
parasympathetic nervous system activation increases it, sympathetic reduces it
glucagon and insulin
hormones secreted by islets of Langherhans in pancreas
glucagon responds to low blood sugar, causing release of glucose and fats into the blood stream, insulin has opposite effect of glucagon, removing glucose from blood for storage as glycogen and fat
liver function
secretes bile, which emulsifies large fat particles in the duodenum, also processes absorbed nutrients, can release free glucose into blood stream
functions in lipid metabolism
hepatocytes and their functions
liver cells that extract nutrients from blood
ghrelin and leptin
ghrelin stimulates appetite while leptin acts as an appetite suppressant
vitamins
must be include in diet, since they can’t be synthesized in the body, divided into fat soluble and water soluble categories
proximal convoluted tubule function
where most of the reabsorption occurs in the part of the tubule nearest to Bowman’s capsule
renal cortex
outer layer of the kidney
where does loop of Henle lead to?
the distal convoluted tubule, which dumps into a collecting duct.
vasa recta function
forms a loop that maintains a high concentration of salt in the medulla, they return to the bloodstream any water that is reabsorbed from the filtrate
What is GI muscle made of
two layers of Smooth muscle, one that is longitudinal and one that is circular
What does it mean that GI smooth muscle is a functional syncytium?
When one cell has an action potential and contracts, the impulse spreads to neighboring cells
sphincter of Oddi
the orifice in which the bile duct and the pancreatic duct empty into
what is bile made of?
bile acids made from cholesterol in the liver
What is true about duodenal pH?
It must be kept neutral or even slightly basic for pancreatic digestive enzymes to function
What hydrolases are in the pancreas?
amylase, lipase, nuclease, and proteases
hepatic portal system function
helps liver process absorbed nutrients
- liver receives oxygenated blood from hepatic arteries
- Liver receive veinous blood draining the stomach and intestine through the hepatic portal vein
chylomicrons
molecules in which lipids exit the intestine and enter the lymphatic system, degraded into chylomicron remnants, taken up by hepatocytes, and combined with protein to make lipoproteins
