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Lesson # 20. The Urinary System-1. Chapter 26. Objectives:. 1- D escribe the organs of the urinary system . 2- D escribe 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 .

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Lesson # 20

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Lesson 20

Lesson # 20

The Urinary System-1

Chapter 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.


Lesson 20

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.


Lesson 20

Overview of the Urinary System


Lesson 20

T11

T12

L1

L2

L3

The Kidneys

Location

  • 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.


Lesson 20

Parietal peritoneum

Renal fascia

Adipose capsule

Renal capsule

External Anatomy of the Kidneys

Stomach

Pancreas

Hylus

Renal artery

Spleen

Renal vein

Kidney

Ureter

It anchors the kidney to the abdominal wall.

It helps protect the kidneys from trauma and maintains the kidneys in place.

It protects the kidneys from trauma and infections.


Lesson 20

Renal column

Cortex

Medulla

Renal pyramids

Renal sinus

Renal lobe

Minor calyx

Major calyx

Ureter

Renal pelvis

Sectional Anatomy of the Kidneys

Blood vessels

Parenchyma

Renal papilla


Lesson 20

Afferent arteriole

Afferent arteriole

Venules

Efferent arteriole

Peritubular capillaries

Arcuate artery

Nephron

Interlobar artery

Interlobar vein

Interlobular or cortical radiate arteries

Interlobular or cortical radiate veins

Interlobular or cortical radiate arteries

Interlobular or cortical radiate veins

Segmental artery

Renal artery

Renal vein

Blood Supply of the Kidney

Arcuate vein

Arcuate vein


Lesson 20

Cortical nephron

Glomerulus

Afferent arteriole

Juxtamedullary nephron

Venule

Efferent arteriole

Cortex

It receives most of the total renal blood flow

Peritubular

capillaries

Cortical radial vein

Cortical radialartery

Corticomedullary junction

Arcuate artery

Arcuate vein

Medulla

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

Vasa recta


Lesson 20

Flow Chart of Renal Circulation

Aorta

Inferior vena cava

Renal a.

Renal v.

Segmental a.

Interlobar a.

Interlobar v.

Arcuate a.

Arcuate v.

Cortical radiate a.

Cortical radiate v.

Afferent arteriole

Peritubular capillaries

Vasa recta

Juxtamedullary nephron

Glomerulus

Efferent arteriole


Lesson 20

The Nephron

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

Renal Corpuscle

- Glomerulus

Parietal layer (simple squamous epithelium)

- Glomerular (Bowman) capsule

Visceral layer (podocytes)

Capsular space

Renal Tubule

Nephron

Renal Tubule

Proximal convoluted

tubule (PCT)

Distalconvoluted

tubule (DCT)

Renal Corpuscle

- Proximal convoluted tubule (PCT)

- Nephron loop (loop of Henle)

- Distal convoluted tubule (DCT)

Glomerulus

The Collecting System

Glomerular capsule

The collecting duct receives fluids from the distal convoluted tubules of several nephrons as it passes back into the medulla.

Collecting

duct (CD)

  • Numerous collecting ducts converge toward the tip of the medullary pyramid to form a papillary duct.

Nephron loop (loop of Henle)

About 30 papillary ducts end in the tip of each papilla


Lesson 20

Nephron

Renal tubule

Renal corpuscle

Collecting duct

Connecting tubules


Lesson 20

Bowman’s capsule

Parietal layer

(Simple squamous epithelium)

Glomerulus

Arterial capillaries (Fenestrated endothelium)

Pedicels & filtration slits

Visceral layer

(Podocytes)

The Renal Corpuscle

Efferent arteriole

Capsular space

Filtrate

Proximal convoluted tubule

Distal convoluted tubule

Afferent arteriole


Lesson 20

Fenestrated endothelium of capillaries

The Filtration Membrane

Podocytes

Capsular Space

Filtration slits

Pedicels

Dense layer

Pedicels

Filtration slits

Filtrate

Fenestrated endothelium of capillaries

Filtrate

Blood

Mesangial cells

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

Capsular Space

Blood

Capsular epithelium

Filtration Membrane:

Visceral layer

1- Fenestrated endothelium of glomerular capillaries

2- Dense layer

3- Filtration slits

Capsular epithelium


Lesson 20

The Juxtaglomerular Complex

Juxtaglomerular Complex:

1- Macula densa

They contain chemoreceptors that monitor the concentration of sodium.

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.

Proximal

convoluted

tubule (PCT)

Distal

convoluted

tubule (DCT)

Renal Corpuscle

2- Juxtaglomerular cells

Distal

convoluted

tubule (DCT)

They contain mechanoreceptors that monitor blood pressure and volume. They contain granules of renin.

Afferent arteriole

Collecting

duct (CD)

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

Nephron loop (loop of Henle)


Lesson 20

The Renal Tubule

Proximal convoluted tube

Distal convoluted tube

Connecting tubule

Collecting duct

Descending limb

Ascending limb

Papillary duct

Loop of Henle


Lesson 20

The Ureters

They extend from the renal pelvis to the urinary bladder .

Renal pelvis

Ureter

Kidneys and ureters are retroperitoneal organs.

Histology

1- Inner mucosa (transitional epithelium + lamina propria).

2-Middle smooth muscle layer.

3-Outer connective tissue layer continuous with the peritoneum.


Lesson 20

The Urinary Bladder

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.

Histology

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.


Lesson 20

The Urethra

Transitional epithelium


Lesson 20

The Urethra


Lesson 20

The Male Urethra

The 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.

Prostate

gland

Prostatic

urethra

Urogenital diaphragm

Membranous

urethra

Spongy (penile)

urethra

Corpus spongiosum


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