MCAT Biology: Renal and Digestive systems

major excretory organs

colon, liver, kidneys

colon function

eliminates solid waste (material that is not eaten but not absorbed into the blood)

liver function

Eliminates hydrophobic waste (material that is eaten and absorbed into the blood but too hydrophobic to dissolve in the plasma)

kidney function

Eliminate hydrophilic waste (material that is eaten and absorbed into the blood and dissolved in the plasma). Filters blood, regulates blood pressure, pH, osmolarity, volume and ion concentration.

main urinary organs

kidney, ureter, bladder, and urethra

adrenal glands

a pair of endocrine glands that sit just above the kidneys

adrenal gland medulla secretes

epinephrine

The adrenal gland cortex secretes

cortisol and aldosterone (A cort)

smooth muscles in the urinary tract

ureter, bladder, urethra, and internal urinary sphincter

skeletal muscles in the urinary tract

external urinary sphincter

kidney cortex

outermost layer of the kidney that has a normal osmolarity

kidney medulla

The deeper region of the kidney contains the loop of Henle regions of the nephrons. Increasing osmolarity towards the center

renal pelvis

central collecting region in the kidney

the three processes to produce urine

filtration, reabsorption, secretion

filtration

moving blood plasma across the glomerulus membrane using blood pressure

reabsorption

Move a substance (ions, bicarbonate, glucose, amino acids, water) from the filtrate to the blood

secretion

move a substance (drugs, toxins, creatine, protons, nitrogen waste) from the blood to the filtrate

afferent arteriole

The small artery that carries blood toward the capillaries of the glomerulus.

efferent arteriole

The small artery that carries blood away from the capillaries of the glomerulus.

glomerulus

a small network of capillaries encased in the upper end of a nephron, where the filtration of blood takes place

vasa recta

capillary bed that surrounds the nephron. all molecules reabsorbed or secreted are from the vasa recta

proximal convoluted tubule

The first section of the renal tubule that the blood flows through; reabsorption of water, ions, and all organic nutrients, as well as secretion of H+, nitrogen waste, and drugs.

descending loop of henle

The increasing osmolarity in the medulla causes water to exit the loop, increasing the osmolarity of the filtrate.

ascending loop of henle

Portion of the nephron not permeable to water. A filtrate flows up the ascending loop through a decreasing concentration of the medulla, salt (NaCl) is actively pumped out of the filtrate, decreasing the filtrate concentration

distal convoluted tubule

Between the loop of Henle and the collecting duct, Selective reabsorption and secretion occur, most notably to regulate the reabsorption of Ca2+

collecting duct

The portion of the nephron where water reabsorption is regulated via antidiuretic hormone (ADH); ADH levels = blood osmolarity

comparing urine and blood

Whatever is happening in the urine, the opposite is happening in the blood

Whatever is happening to volume, the opposite is happening to concentration/molarity

renin-angiotension system

If blood pressure falls, kidney secretes renin. Renin converts angiotensinogen to angiotensin I. ACE converts angiotensin I to angiotensin II which causes systemic vasoconstriction and an increase in aldosterone release

aldosterone on blood pressure

increases the number of Na+/K+ ATPases in the nephron to increase blood osmolarity. ADH causes water reabsorption to increase blood volume and pressure.

Juxtaglomerular apparatus

contact point between the afferent arteriole and the distal convoluted tubule. The afferent arteriole is a baroreceptor and senses when pressure is low. The distal tubule is a chemoreceptor that senses when the filtrate is low and causes the release of renin and the dilation of the afferent arteriole.

ANP blood pressure regulation

High blood pressure causes the atria of the heart to stretch, causing the right atrium to release atrial natriuretic peptide. ANP causes vasodilation and inhibits renin and aldosterone release.

Kidney pH regulation

secretes H+ or reabsorbs bicarbonate to engage in the blood buffer system as needed

SNoW DRoP

Southern- DNA

Northern- RNA

Western- Protein

alimentary canal

digestive tube that extends from the mouth to the anus

accessory organs

feed into the alimentary canal

role of bile

EMULSIFICATION of fats. The breakdown of large lipid globules assists in their absorption

gallbladder function

store and concentrate bile and releases bile due to CCK release from small intestine

endocrine role of pancreas

to secrete insulin and glucagon into the bloodstream to help regulate blood glucose levels.

Exocrine role of the pancreas

releases bicarbonate, and various pancreatic digestive enzymes (proteases, lipases, etc.),

pancreatic protease activation

trypsinogen is activated by enterokinase produced by small intestine

mucosa

An innermost layer of the alimentary canal wall breaks down food and absorbs nutrients. Protection from harmful ingested products and produces mucus to lubricate.

submucosa

layer of connective tissue under the mucosa in the alimentary canal wall. Blood vessels absorb amino acids and sugars to deliver them to the liver via the hepatic portal vein. where lymph vessels absorb fats

enteric nervous system

The nervous system of the gastrointestinal tract. It controls secretion and motility within the Gi tract and is linked to the central nervous system.

circular muscle

layer of muscle around the alimentary canal wall that mixes food with digestive juices and segments them into bolus

longitudinal muscle

The outer layer of smooth muscle in the wall of the digestive tract. When the longitudinal muscle contracts the tube shortens (peristalsis)

peristalsis

Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.

function of the mouth

mastication, taste food, form a bolus, lubrication

components of saliva

lysozyme: kill bacteria, amylase: startch digestion, lingual lipase: fat disgestion

function of the esophagus

Moves food from the mouth to the stomach. Begins as skeletal muscle then becomes smooth muscle

cardiac sphincter

at the connection between the esophagus and stomach that keeps food in the stomach. By the heart.

function of the stomach

store food and slowly release to small intestine, also to digest polypeptides into tri and di peptides.

gastric glands

Exocrine glands in the stomach wall that secrete gastric juice into the stomach. made up of mucus cells, parietal cells, and chief cells

pyloric sphincter

connects the stomach to the small intestine and regulates release

parietal cells

exocrine secretion of HCl into the stomach

chief cells

exocrine secretion of pepsinogen (further activated by HCl)

G cells

endocrine secretion of gastrin due to the presence of food. This increases the activity of salivary and gastric glands and increases the GI tract motility

function of the small intestine

break nutrients into monomers and absorbs them

regions of the small intestine

duodenum (first 5%), jejunum (middle 40%), ileum (last 55%)

surface area of the small intestine

HUGE due to plicae folds in mucosa, villus folds in the plicae and microvilli folds in the villus

enterokinase

exocrine secretion of the small intestine that triggers the activation of pancreatic proteases from the zymogen form (trypsinogen to trypsin)

brush border enzymes

exocrine digestive enzymes from the small intestine

enterogastrone

endocrine secretion of small intestine due to large meal and will slow digestion

CCK

endocrine secretion of the small intestine released to due to fats and triggers the release of bile from the gallbladder

Secretin

endocrine secretion of the small intestine that is released due to low pH and causes the pancreas to release bicarbonate.

function of the large intestine

store and form feces and reabsorb water when dehydrated

bacteria in the large intestine

The body's "natural flora" prevents the spread of bad bacteria. Produces 50% of vitamin K (for clotting) and gas

ileocecal valve

regulates the movement from the small to large intestine

internal/external anal sphincters

Regulate the release of feces. smooth/skeletal muscle control