Anatomy of the Urinary System

Kidneys

Ureters

Bladder

Urethra

The Kidneys

Functions of the Kidneys:

- removal of waste products from blood

- control of blood volume

- control of salt balance in blood

- control of pH of the blood (acid-base balance)

Gross Anatomy of the Kidneys

The kidneys are bean-shaped organs located on the posterior abdominal wall

Gross Anatomy of the Kidneys

Kidneys are retroperitoneal

Kidneys are covered by a renal capsule, and enclosed in a renal fat pad

The kidney and associated fat pad are enclosed by renal fascia

Gross Anatomy of the Kidneys

Renal hilus: site where renal artery enters and renal vein and ureter leave the kidney

Internal structures:- cortex- medulla (pyramids)- renal columns- renal papillae- minor calyx- major calyx- renal pelvis-ureter

renal pelvis

hilus

ureter

renalpapilla

renal capsule

renalcolumns

majorcalyx

renal pyramids

minorcalyx

cortex

medulla

Renal Blood Supply

Blood goes to the kidney in the renal artery, which branches into segmental arteries as it enters the hilus

Segmental arteries branch into interlobar arteries, which become arcuate arteries as they curve over the base of the renal pyramids

Arcuate arteries give off interlobular arteries in the cortex, from which branch the afferent arterioles (to the nephron)

Efferent arterioles carry blood away from the nephron, into the peritubular capillary network

The capillaries drain into interlobular veins, which drain into arcuate, interlobar, and renal veins

Renal Blood Supply

renal artery

renal vein

segmentalartery interlobar

arteries

interlobulararteries

interlobar veins

arcuate veins

arcuate arteries

interlobularartery

arcuateartery

interlobar vein

interlobar artery

Histology of the Kidney

The basic functional unit of the kidney is the nephron

The nephron is composed of:

- renal corpuscle

- Bowman’s capsule

- glomerulus (capillary tuft)

- proximal convuluted tubule

- Loop of Henle

- distal convuluted tubule Each nephron is connected to a collecting

duct

renalcorpuscle

proximalconvuluted

tubule

distalconvuluted

tubule

descendinglimb

ascendinglimb

collectingduct

Location of Functional Units

Nephrons are located primarily in the cortex; Loops of Henle extend into medullary pyramids

Juxtamedullary nephrons are located near medulla, have longer Loops of Henle

Collecting ducts are found in the medullary pyramids, and empty urine into the renal papillae

Renal Corpuscle

The renal corpuscle (site of filtration) is composed of Bowman’s capsule and the glomerulus

Bowman’s capsule is double-walled structure

Podocyte cells glomerulus: capillary tufts gaps in epithelium: fenestrae juxtaglomerular cells: renin macula densa

parietal epithelium

podocyte

glomerularcapillary

afferentarteriole

efferentarteriole

DCT

macula densa

juxtaglomerularcells

The Ureters

Function: carry urine from the kidneys to the bladder

Histology: three layers to ureter wall

- mucosa: transitional epithelium, lamina propria

- muscularis: inner longitudinal, outer circular, outermost longitudinal in lowest 1/3rd

- adventitia Enter bladder as narrow slit-like

opening

The Bladder

Function: storage of urine Located in pelvic cavity, posterior to

the pubic symphysis Histology: mucosa, muscularis, and

adventitia, as in ureters (thicker muscularis in bladder)

Specialization of internal bladder wall: trigone

Internal urinary sphincter: smooth muscle at junction of bladder and urethra

External urinary sphincter: skeletal muscle

Urethra

In the male, three named parts:

- prostatic

- membranous

- spongy

Urethra

In the female, the urethra is much shorter:

Next Lecture.....

Physiology of the Urinary System