URINARY SYSTEM

Lecturer Dr.Firdous M.Jaafar

Department of anatomy/Histology

section

Lecture 1

objectives

1- Describe the different parts of urinary system.

2- Describe the structure of kidney.

3- Define nephron, and list its histological parts.

a- Define renal corpuscle, describe its structure, and name

its parts.

b- Define Podocyte, and relate between its histological

structure and process of filtration.

c- Define filtration slit, describe its structure, and list its

components.

4- Recognize some clinical problems related to filtration.

5- Describe Mesangial cell, and identfy some of its functions.

Urinary system

• Consists of two kidneys, ureters, and one bladder

and ureter.

• Function:

• 1- Filtration of cellular wastes from blood

• 2- Selective reabsorption of water and solutes

• 3- Excretion of the wastes and excess water as

urine.

Structure of kidney

Structure of renal lobe

Renal papilla

nephron

The major divisions of each nephron are:

• Renal corpuscle, an initial dilated portion in the cortex

• Proximal convoluted tubule, located primarily in the

cortex

• Thin and thick limbs of the nephron loop (loop of Henle),

which descend into the medulla, then ascend back to the

cortex

• Distal convoluted tubule

• Collecting tubule.

nephron

Renal corpuscle

Glomerular capillary

rrRenal corpuscle/Podocyte

Podocyte

Podocyte SEM

Podocyte/TEM

Filtration apparatus

• Consists of:

• 1- Endothelium of glomerular capillaries: they

are fenestrated, with no diaphragm, and posse a

large number of aquaporin-1(AQP-1) water

channels that allow fast movement of water

through epithelium.

• 2- Glomerular basement membrane.

• 3- Podocytes.

• Medical applications;

• In diseases such as diabetes mellitus and

glomerulonephritis, the glomerular filter is

altered and becomes much more permeable

to proteins, with the subsequent release of

protein into the urine (proteinuria).

Mesangial cell

Mesangial cell TEM

Functions of mesangial cell

• Physical support and contraction—the mesangium

provides internal structural support to the glomerulus and

like pericytes, its cells respond to vasoactivesubstances

to help maintain hydrostatic pressure for the optimal rate

of filtration.

• Phagocytosis—mesangial cells phagocytose protein

aggregates that adhere to the glomerular filter, including

antibody-antigen complexes abundant in many

pathological conditions.

• Secretion—the cells synthesize and secrete several

cytokines, prostaglandins, and other factors important for

immune defense and repair in the glomerulus.