Urinary system

Course: B.Sc.(Micro./Biotech) sem IISubject: Animal & Plant Physiology

Unit 2.2

Functions of Urinary System

• Kidneys carry out four functions– Filter nitrogenous wastes, toxins, ions, etc. from blood to

be excreted as urine.– Regulate volume and chemical composition of blood

(water, salts, acids, bases).– Produce regulatory enzymes.

• Renin – regulates BP/ kidney function • Erthropoeitin – stimulates RBC production from marrow.

– Metabolism of Vitamin D to active form.

Urinary System

• Two Kidneys– Perform all functions except actual excretion.

• Two Ureters– Convey urine from Kidneys to Urinary Bladder

• Urinary Bladder– Holds Urine until excretion

• Urethra– Conveys urine from bladder to outside of body

Complete System

1

Kidney general info

• Lie against posterior abdominal wall • Right kidney is lower than left kidney due to the

shape of the liver.• Lateral surface of kidney is convex while medial is

concave.– Concave side has a cleft – Renal Hilus– Inside hilus is Renal sinus

• Where kidneys receive renal vessels and nerves.

Kidney External Anatomy

• Average size – 12cm x 6cm x 3 cm• Weights 150 grams or 5 oz• Surrounded by three membranes (deep to

superficial)– Renal capsule – fibrous barrier for kidneys.– Adipose capsule – fatty tissue designed for protection /

stability.– Renal fascia – dense fibrous CTP anchors kidneys/

adrenals/ membrane 1 and 2 to surroundings.

Kidney Anatomy

• Renal arteries and veins• Renal cortex• Renal medulla• Nephron• Renal pyramids (6-10)• Renal papilla• Calyx (ces)• Renal pelvis• Ureter

Kidney- External Anatomy

• Lateral surface- convex • Medial is concave-– Renal Hilum• Opening to Kidney

– Renal Sinus• Space within hilus• Kidneys receive blood vessels and nerves. 2

Kidney Internal Anatomy I

• Renal arteries and veins– Bring blood in and out of kidney

• Renal cortex– Outer layer of Kidney

• Renal medulla– Inner layer of Kidney

• Nephron

Kidney Internal Anatomy II

• Renal Pyramids• Renal Columns

– Space between pyramids within the medula

• Renal Papilla– Narrow end of pyramid

• Calyx (ces)– Collecting tubes

• Renal Pelvis– Collecting vessel prior to ureter

3

Nephron

• Blood processing unit which serves to produce urine

• 1 million per kidney• Consists of a glomerulus and tubules• Two part: – Renal corpuscle : blood plasma is filtered

• glomerulus( capillary network)• Glomerulus capsule(Bowman’s)

– Renal tubule: filtered fluid passes.

Nephron: Vascular System

• Afferent arteriole• Glomerulus• Efferent arteriole• Peritubular

capillaries– Capillary beds

reabsorb in cortex

4

Nephron• Tubular system– Glomerular Capsule– Proximal convoluted tubule– Loop of Henle (nephron loop)• Descending limb• Ascending limb

– Distal convoluted tubule– Collecting duct

Nephron

5

6

Urine Formation I

• Glomerular filtration• Water, ions, amino

acids, and glucose get into capsular space from blood

• Proteins stay in blood – too big to leave capillaries.

Urine Formation II

• Proximal convoluted tubule and Peritubular capillary

• Na+ goes down gradient and brings glucose, amino acids, etc. back into blood stream (cotransport).

• Reabsorbs about 65% of filtrate.

7

Urine Formation III

• Descending limb

• Goes into medulla - increasing salt gradient

• Water leaves• Fluid concentrates

• Ascending limb

• Goes up toward cortex - decreasing salt gradient

• Na+ pumped out• Fluid relatively diluted

Countercurrent Multiplicationin the Nephron Loop

Nephron Loop

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Urine Formation IV

• Collecting duct• Travels down into medulla• Water leaves tubule and enters blood• Urine becomes concentrated and enters renal

papilla• ADH controls water channel• ADH – Antidiuretic hormone

Collecting duct

9

Dynamic Human

Urine Formation

Micturition

• Ureters– 25 cm long– Enters on the floor of bladder

• Urinary Bladder– Muscular sac on floor of pelvic cavity– Muscle layer formed by detrusor muscle– Average bladder volume is 500 ml– Max capacity is 700-800 ml

Micturition

• Urethra– Conveys urine out of body– Female urethra – 3 - 4 cm– Opens into external urethral oriface– Lies between vaginal oriface and clitoris– Male urethra – 18 cm– 3 regions

• Prostatic urethra – 2.5 cm• Membranous urethra – 0.5 cm• Penile urethra – 15 cm

Micturition Reflex

Bladder with >= 200 ml of urine

Sensory input to parasympathetic system

Contraction of detrusor muscle and relaxation of internal urethral sphincter

Relaxation of external urethral sphincter

Micturition

10

Kidney stones

• A hard granule of calcium, phosphate, uric acid and protein.

• Form in renal pelvis and get lodged in pelvis or ureter.

• Caused by urinary tract infections, dehydration, pH imbalances, or an enlarged prostate gland.

• Treated with stone dissolving drugs, surgical removal, or lithotripsy (ultrasonic vibrations)

References:Image 1: http://postimg.org/image/rbccc1f7t/Image 2: http://postimg.org/image/kkr9ov2o9/Image 3: http://postimg.org/image/a0hc69y6h/Image 4: http://postimg.org/image/87efhyczt/Image 5: http://postimg.org/image/8rtgkn689/Image 6: http://postimg.org/image/qgl7c9hzd/Image 7: http://postimg.org/image/5nisnupft/Image 8: http://postimg.org/image/zac3td4y1/Image 9: http://postimg.org/image/fpxkql4cp/Iamge 10: http://postimg.org/image/mhnztftc9/Book: 1. Human Physiology 4th edition by Lauralee Sherwood