Lesson # 20 The Urinary System-1Chapter 26

Objectives:

1- Describe the organs of the urinary system .2- Describe the location and structural features of the kidneys.3- Describe the structure of a nephron.4-Trace the path of the blood flow through a kidney.5- Describe the structure of ureter, urinary bladder and urethra.

Functions of the Urinary System

1- Regulates blood composition and blood pressure, as well as body fluid composition and volume.2- Regulates blood pressure by releasing rennin, which activates the rennin-angiotensin mechanism that raises the blood pressure.3- Regulates some metabolic reactions by converting vitamin D to its active form.4- Releases erythropoietin, which increases production of red blood cells.5- Helps to regulate blood pH by controlling the loss of hydrogen and bicarbonate ions in the urine.

6- Helps to regulate calcium ion levels by producing calcitriol.

Overview of the Urinary System

T11T12L1L2L3

Location

The Kidneys

The kidneys lie against posterior abdominal wall at level of T12 to L3.

They are retroperitoneal along with ureters, urinary bladder, renal artery and vein, and adrenal glands.

Kidney

Stomach

Spleen

PancreasParietal

peritoneum

Renal capsuleAdipose capsule

Renal fascia

Hylus

External Anatomy of the Kidneys

Renal arteryRenal veinUreter

It protects the kidneys from trauma and infections.

It helps protect the kidneys from trauma and maintains

the kidneys in place.

It anchors the kidney to the abdominal wall.

Sectional Anatomy of the Kidneys

Renal sinus

Cortex

MedullaRenal pyramids

Renal column

Minor calyx

Major calyx

Renal pelvisUreter

Renal lobe

Blood vessels

Renal papilla

Parenchyma

Blood Supply of the Kidney

Renal artery

Segmental artery

Interlobar artery

Arcuate artery

Interlobular or cortical radiate

arteries

Afferent arteriole

Nephron

Arcuate vein

Interlobar vein

Renal vein

Interlobular or cortical radiate veins

Interlobular or cortical radiate arteries

Afferent arterioleEfferent arteriolePeritubular capillariesVenules

Interlobular or cortical radiate veins

Arcuate vein

Arcuate artery

Cortical radial artery

Afferent arteriole

Glomerulus

Efferent arteriole

Peritubularcapillaries

Cortical radial vein

Arcuate vein

It receives most of the total renal blood flow

It receives 1% to 2% of the total renal blood flow

Corticomedullary junction

Cortex

Medulla

Cortical nephron

Juxtamedullary nephron

Vasa recta

Venule

Flow Chart of Renal

Circulation

Inferior vena cava

Arcuate v.

Peritubular capillaries Vasa recta

Efferent arteriole Glomerulus

Afferent arteriole

Cortical radiate a.

Arcuate a.

Interlobar a.

Segmental a.

Renal a.

Aorta

Cortical radiate v.

Interlobar v.

Renal v.

Juxtamedullary nephron

The NephronThe nephrons are the functional units of the kidneys. Each kidney has about 1.2 million nephrons

Renal Corpuscle

Renal Tubule

- Glomerulus

- Glomerular (Bowman) capsuleNephron

Parietal layer (simple squamous epithelium)Visceral layer (podocytes)Capsular space

- Proximal convoluted tubule (PCT)- Nephron loop (loop of Henle) - Distal convoluted tubule (DCT)

The collecting duct receives fluids from the distal convoluted tubules of several nephrons as it passes back into the medulla. Numerous collecting ducts converge toward the tip of the medullary pyramid to form a papillary duct.About 30 papillary ducts end in the tip of each papilla

Renal Corpuscle

Proximal convolutedtubule (PCT)

Nephron loop (loop of Henle)

Distal convolutedtubule (DCT)

Collectingduct (CD)

The Collecting System

Renal Tubule

Glomerulus

Glomerular capsule

Nephron

Renal corpuscle

Renal tubule

Collecting duct

Connecting tubules

The Renal Corpuscle

Capsular space

Visceral layer(Podocytes)

Pedicels & filtration slits

Afferent arteriole

Efferent arteriole

Proximal convoluted

tubule

Bowman’s capsuleGlomerulus

Parietal layer(Simple squamous

epithelium)Arterial

capillaries (Fenestrated endothelium)

Distal convoluted

tubule

Filtrate

The Filtration Membrane

PodocytesPedicels

Filtration slitsFenestrated endothelium of capillaries

Mesangial cells

Blood

Capsular Space

Filtrate

They control the capillary diameter and the rate of capillary blood flow.

Visceral layer

Capsular epithelium

Capsular epithelium

Blood

Fenestrated endothelium of capillaries

Capsular Space

Filtration slits

Pedicels

Dense layer

Filtrate

3- Filtration slits2- Dense layer

1- Fenestrated endothelium of glomerular capillaries

Filtration Membrane:

Renal Corpuscle

Proximalconvoluted

tubule (PCT)

Nephron loop (loop of Henle)

Distalconvoluted

tubule (DCT)

Collectingduct (CD)

Distalconvoluted

tubule (DCT)

They contain chemoreceptors that monitor the concentration of sodium.

1- Macula densa

2- Juxtaglomerular cellsThey contain mechanoreceptors that monitor blood pressure and volume. They contain granules of renin.

The Juxtaglomerular Complex

Juxtaglomerular Complex:

If the flow of tubular fluid increases and sodium concentration decreases, the macula densa stimulates JG cells contract which constricts afferent arteriole, reducing the glomerular filtration.

If blood pressure decreases, the renin is released producing a vasoconstriction that raises the blood pressure.

Afferent arteriole

The Renal Tubule Proximal convoluted

tube

Distal convoluted

tube

Loop of Henle

Descending limb

Ascending limb

Collecting duct

Papillary duct

Connecting tubule

The UretersThey extend from the renal pelvis to the urinary bladder .

Renal pelvis

Ureter

Kidneys and ureters are retroperitoneal organs.

1- Inner mucosa (transitional epithelium + lamina propria).2-Middle smooth muscle layer.

3-Outer connective tissue layer continuous with the peritoneum.

Histology

The Urinary Bladder

1- Inner mucosa (transitional epithelium + lamina propria) with folds called rugae.2- Middle layer: Detrusor muscle (Inner and outer layers of longitudinal smooth muscle, and a circular layer between the two).3-Outer connective tissue layer continuous with the peritoneum.

Histology

The urinary bladder is in the pelvic cavity and it is covered by a layer of peritoneum (visceral peritoneum).

Function: It is a temporary reservoir for the storage of urine.

Transitional epithelium

The Urethra

The Urethra

The Male UrethraThe male urethra is about 8 cm long and it is shared by the urinary and reproductive systems.It consists of three regions: prostatic, membranous, and spongy (penile) urethra.

Prostategland

Prostaticurethra

Membranousurethra

Corpus spongiosum

Spongy (penile)urethra

Urogenital diaphragm