A&P urinary system

functions of the urinary system

• fluid, electrolyte, and pH balance

• adjusting blood volume and BP

• removing drugs, toxins, and nitrogenous wastes

• regulation of plasma concentration and blood pH

location of the kidneys

lateral to the vertebral column, between muscles of dorsal body wall and the peritoneum.

what holds the kidneys in place?

• peritoneum

• contact and adjacent organs

• 3 concentric layers of CT

3 concentric layers of CT of kidney

renal capsule, adipose capsule, and renal fascia.

function of the kidneys

excretion of nitrogenous wastes, water, electrolytes, and by product of some drugs.

outer portion of the kidney

solid, location of nephrons, has 2 regions (cortex and medulla)

renal cortex

contains PCT, DCT, glomerulus, and most nephrons

renal medulla

with renal pyramids, papilla, and columns: contain collecting ducts and loops of henle.

inner portion of the kidney

contains renal pelvis, surrounded by the renal sinus

function of renal pelvis

collect urine form major and minor calyces.

function of the arteries in the kidney

carries blood from abdominal aorta to each kidney. Has afferent and efferent arterioles.

afferent arterioles

carry blood to glomerulus of each nephron

efferent glomerulus

carry blood away from glomerulus of each nephron.

function of the capillaries in the kidney

surround the proximal and distal tubules as well as the loop of henle

function of the veins in the kidney

carry blood away from the kidney, back to the inferior vena cava

how much of your cardiac output do your kidneys receive?

20-25%

structures of the nephron

• renal corpuscle

• proximal convoluted tubule

• nephron loop

• distal convoluted tubule

• collecting duct

what makes up the renal corpuscle?

glomerulus and Bowmans capsule (surrounding glomerulus)

structures within the loop of henle

descending limb and ascending limb (thin and thick segments).

filtration

water, nutrients, and wastes leave blood vessels of the glomerulus and enters the glomerular capsule.

reabsorption

mainly done by the proximal convoluted tubule. Nutrients and water are reabsorbed back into the blood.

Secretion

mainly done by the distal convoluted tubule. Any wastes still in the blood are actively secreted.

concentration of urine

done by the loop of henle and collecting duct. More reabsorption of water back into blood.

structures within the filtration membrane

• capillaries of glomerulus have fenestrated endothelium

• basement membrane

• filtration slits

basement membrane function

very small, plus a negative charge that “holds back” many proteins

filtration slits function

even smaller than BM, between pedicels of podocytes, molecules cant cross.

juxtaglomerular appartatus is composed of:

• JG cells of the afferent arteriole

• Macula dense of the DCT

• mesangial cells

JG cells of the afferent arteriole function

release renin and cause constriction of afferent arteriole.

macula dense of the DCT function

stimulate the JG cells and respond to changes in the composition of fluid in the DCT

histology of a nephron

• simple cuboidal in the PCT and DCT

• simple cuboidal and simple squamous in the loop of henle and collecting ducts.

ureters structure

muscular tube with a slit-like opening to the bladder that helps prevent back flow.

urinary bladder histology

• inner mucosa with transitional epithelium and lamina propria

• muscularis with 3 layers of smooth muscle

internal urethral sphincter

involuntary control

trigone

acts as a funnel that helps direct urine into the urethra.