A.
II. Purpose- excrete or remove waste products of metaolish toprevent self poisoning. Types of wastes
include
A.
B.
C.
D.
III. Function of kidney
A. Eleminate nitrogenous wastes, toxins, drugs
B. Maintain pH balance and salt balance- important for muscle contraction, action potentials,
membrane permeability, etc..
C. Regulate water content
D. Produce ormne erythropoietin- stimaulate RBC production in bone marrow.
IV. Kidney- chief organ of excretion in land dwelling organisms
A. External features
1. Shape, size and location-bean shaped, size of your fist, and located at the posterior abdominal
wall.
2. Coverings
a. Renal fascia
b. Adipose
c. Renal capsule
B. Internal Structure
1. Hilium
2. Renal Pelvis
3. Calyces
4. Layers
a. Renal Medulla
b. Renal Cortex
C. Blood Supply
1. Arterial system-from dorsal aorta to
a. Renal Arteries-these vessels handle 1/4 the total cardiac output (1200 ml) every
minute.
b. Lobar arteries-five branch off the renal artery.
c. Interlobar arteries-extend between the renal pyramids.
d. Arcuate arteries-extend between cortex and medulla.
e. Interlobular arteries-extend from the arcuate arteries into the cortex.
f. Afferent arterioles-lead to the nephrons.
2. Venus system
a. Efferent arteriole
b. Interlobular vein
c. Arcuate vein
d. Interlobar vein
e. Lobar vein
f. Renal vein
D. Nephron Structure-
1. Renal corpuscle-
a. Bowman's capsule
b. Glomerulus-capillary network. Walls of capillaries contain large pores called fenestrae that allow blood to be filtered. Specialized cells called podocytes encircle capillaries and allow materials to be filtered through filtration slits.
2. Renal tubule-
a. Proximal convoluted tubule-
b. Loop of Henle-
-Descending loop
-Ascending loop
c. Distal convoluted tubule
d. Collecting duct
E. Blood Flow Through Nephron-proceeds from afferent arteriole to glomerulus to efferent arteriole. Because afferent vessel is larger, fluid "backs up" creating a high pressure system, forcing fluids and solutes out of bloodstream. When pressure is increased, more urine is produced.
V. Nephron Function
A. Urine Formation-involves 3 processes
1. Filtration-involves movement of blood plasma across filtration membrane of glomerulus. Large molecules like proteins, blood cells, etc. cannot cross the filtration membrane and remain within the bloodstream. The substances that pass the membrane constitute the filtrate. 99% of the fluid is recovered, while only 1% is lost.
2. Reabsorption- Filtrate is processied with glucose, bicarbonate ions, amino acids. vitamins. calcium, etc. being recalled into the blood. Movement of these substances occurs in one direction either by osmosis, difusion, active transport, sokium ions by simple diffusion, water by osmosis, etc..
a. Proximal tubule-
b. Loop of Henle (descending tubule)-
c. Loop of Henle (ascending tubule)-
d. Distal tubule and collecting duct-
3. Secretion- some unwanted and harmful substqnces move by active transport or
diffusion
from the peritubular capillaries into the renal tubule(proximal tubule). For example,
hydrogen ions, potassium ions, penicillin are actively transported while urea moves by
diffusion.
B. Urea and Uric Acid excretion- urea and uric acid are toxic to the body and must be removed.
Ammonia is formed in the liver from amino acid metabolish and converted tourea. 50% of
the urea is excreted. Uric acid results from the metabolism of certain nucleic acids and 10%
of it is excreted yb secretion.
C. Regulation of urine concentration-
1. Angotensis II (Aldosterone)- when filtration pressure decreases, Angiotensis is produced
and acts on the adrenal glands to release Aldosterone. This causes increased reabsorption
of sodium, chloride and water out of nephron into the peritubular capillaries. This causes
a decrease in urine production meaning a greater volume of fluid in blood stream which
increases blood pressure.
2. Antidiuretic Hormone- released by the pituitary gland when blood pressure drops. This
hormone causes an increase in the permeability of the distal tubules to water
(reabsorption). As more water is reabsorbed back into the body, blood volume and
pressure is increased. The urine produced is now more concentrated.
3. Atrial Natriuretic Factor (hormone)-