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The Urinary System.

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Presentation on theme: "The Urinary System."— Presentation transcript:

1 The Urinary System

2 Functions of the urinary system
Homeostatic regulation of blood plasma Regulating blood volume and pressure Regulating plasma ion concentrations Stabilizing blood pH Conserving nutrients Filter many liters of fluid from blood Excretion - The removal of organic waste products from body fluids Urea Uric acid Creatinine Elimination - The discharge of waste products into the environment

3 Urinary System Kidneys – produce urine
Ureters –transport urine to bladder Urinary bladder - stores urine Urethra transports urine to exterior Figure 26.1

4 Location and External Anatomy of Kidneys
Located retroperitoneally Lateral to T12–L3 vertebrae Average kidney 12 cm tall, 6 cm wide, 3 cm thick Hilus On concave surface Vessels and nerves enter and exit Renal capsule surrounds the kidney

5 Urinary System in Gross Dissection
Figure 26.3

6 Internal Gross Anatomy of the Kidneys
Frontal section through the kidney Renal cortex Renal pyramids Renal pelvis Major calicies Minor calicies Gross vasculature Renal arteries Branch into segmental arteries

7 Anatomy of the kidneys Superficial outer cortex and inner medulla
The medulla consists of 6-18 renal pyramids The cortex is composed of roughly 1.25 million nephrons Major and minor calyces along with the pelvis drain urine to the ureters

8 Nephron – The Functional Unit of Kidney
Nephron consists of: Renal corpuscle Renal tubule: Proximal convoluted tubule (PCT) Loop of Henle Distal convoluted tubule (DCT) Nephron empties tubular fluid into a system of collecting ducts and papillary ducts

9 Renal Corpuscle Consists of:
Glomerulus – tuft of fenestrated capillaries Glomerular (Bowman’s) capsule Parietal layer – simple squamous epithelium Visceral layer – consists of podocytes Blood travels from efferent arteriole to peritubular capillaries Blood leaves the nephron via the efferent arteriole

10 Renal Corpuscle and the Filtration Membrane
Figure 23.6a

11 Glomerulus anatomy Podocytes cover lamina densa of capillaries
Project into the capsular space Pedicels of podocytes separated by filtration slits

12 Two types of nephron Cortical nephrons Juxtamedullary nephrons
~85% of all nephrons Located in the cortex Juxtamedullary nephrons Closer to renal medulla Loops of Henle extend deep into renal pyramids

13 Nephron Proximal convoluted tubule (PCT) Loop of Henle
Actively reabsorbs nutrients, plasma proteins and ions from filtrate Released into peritubular fluid Loop of Henle Descending limb Ascending limb Each limb has a thick and thin section

14 Nephron Distal convoluted tubule (DCT)
Actively secretes ions, toxins, drugs Reabsorbs sodium ions from tubular fluid

15 Collecting Tubules (Collecting ducts)
Collecting tubules - Receive urine from distal convoluted tubules Figure 23.8

16 Uriniferous Tubule Figure 23.5a

17 Types Of Capillary Beds In Nephron
Glomerulus - Fed and drained by afferent and efferent arterioles Peritubular capillaries Arise from efferent arterioles Low-pressure, porous capillaries Absorb solutes Vasa recta Thin-walled looping vessels Part of the kidney’s urine-concentrating mechanism

18 Mechanisms of Urine Production
Filtration - filtrate of blood leaves kidney capillaries Reabsorption – most nutrients, water, and essential ions reclaimed Secretion - active process of removing undesirable molecules

19 Microscopic Anatomy of the Kidney
Juxtaglomerular apparatus Functions in the regulation of blood pressure Juxtaglomerular cells – secrete renin Macula densa A portion of distal convoluted tubule Tall, closely packed epithelial cells Act as chemoreceptors

20 Summary of Nephron Function
Each segment of nephron and collecting system contribute Glomerulus PCT Descending limb Thick ascending limb DCT and collecting ducts Concentrated urine produced after considerable modification of filtrate

21 Urine Excretion Leaves Collecting System Enters renal pelvis
Rest of urinary system transports, stores and eliminates Ureters Bladder Urethra

22 The Ureters Pair of muscular tubes
Extend from renal pelvis to the bladder Peristaltic contractions force urine from the kidneys to the urinary bladder Oblique entry into bladder prevents backflow of urine

23 Histology of Ureter Mucosa – transitional epithelium
Muscularis – two layers Inner longitudinal layer Outer circular layer Adventitia – typical connective tissue

24 Urinary Bladder A collapsible muscular sac Stores and expels urine
Full bladder – spherical Expands into the abdominal cavity Empty bladder – lies entirely within the pelvis Figure 23.13

25 Urinary Bladder Wall of bladder Mucosa - transitional epithelium
Muscular layer - detrusor muscle Adventitia

26 The urethra Extends from the urinary bladder to the exterior of the body Passes through urogenital diaphragm (external urinary sphincter) Differs in length and function in males and females Internal urethral sphincter - involuntary smooth muscle External urethral sphincter - voluntarily inhibits urination, relaxes when one urinates

27 Urinary Bladder and Urethra - Male
Males – 20 cm in length Three named regions Prostatic urethra - passes through the prostate gland Membranous urethra - through the urogenital diaphragm Spongy (penile) urethra passes through the length of the penis Figure 23.16a

28 Urinary Bladder and Urethra - Female
In females - length of 3–4 cm The smooth triangular region of the base is is called the trigone - many bladder infections persist in this region

29 Urethra Epithelium of urethra
Transitional epithelium at the proximal end (near the bladder) Stratified and pseudostratified columnar – mid urethra (in males) Stratified squamous epithelium at the distal end (near the urethral opening)

30 Micturition Bladder can hold 250 - 400ml
Greater volumes stretch bladder walls initiates micturation reflex: Urination coordinated by micturition reflex Initiated by stretch receptors in wall of bladder Urination requires coupling micturition reflex with relaxation of external urethral sphincter

31 Blood Flow Through the Kidney


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