Urinary system

Question 1

Components of The Urinary System

Answer 1

• Excretory system that filters blood and removes excess fluids, metabolic wastes, and ions
  Macroscopic components:
• Kidneys (2)
• Ureters (2)
• Urinary bladder (1)
• Urethra (1)

Question 2

Location of Kidneys

Answer 2

• The kidneys are retroperitoneal
• Located behind the parietal peritoneum
• The lower ribs offer some protection of the kidneys

Question 3

Functions of the Kidney

Answer 3

• Filter blood, removing metabolic wastes, toxins, and ions
• Regulate volume and chemical makeup of blood
• Balance water, salts, acids, and bases

Question 4

Macroscopic Anatomy of the Kidney

Answer 4

• Kidney is surrounded by a tough, fibrous capsule (dense irregular CT)
• Around this capsule is the perirenal fat capsule

Question 5

What is Internal Anatomy of Kidney?

Answer 5

• The tip of a pyramid is called a papilla
• Urine that is produced in the pyramids drains into a minor calyx
  (calyx = cup)
• Multiple minor calices drain into a major calyx
• The major calices drain into the renal pelvis which drains into the ureter

Question 6

What is the main structural and functional unit of the kidney?

Answer 6

• The main structural and functional unit of the kidney is the nephron
• There are more than a million nephrons in each kidney

Question 7

What is the Nephron Structure?

Answer 7

• Each nephron is composed of a renal corpuscle and a renal tubule
• Renal corpuscle = glomerular capsule + glomerulus (a tuft of capillaries)
• The renal tubule is subdivided into
• Proximal convoluted tubule
• Nephron loop (loop of Henle)
• Distal tubule
• Distal tubule drains into the
  collecting duct
• Many nephrons drain into one collecting duct
• Help concentrate the urine

Question 8

What are Cortical Nephrons

Answer 8

Cortical nephrons
* Make up 85% of all nephrons
* Are located almost entirely within the cortex
* Nephron loops dip into medulla only a short distance

Question 9

What are Juxtamedullary nephrons?

Answer 9

Juxtamedullary nephrons
* Make up 15% of nephrons
* Are called juxtamedullary because the renal corpuscle is near the cortex-medullary border
* Nephron loops dip deeply into medulla
* Long loops help produce concentrated urine

Question 10

What are Peritubular Capillaries?

Answer 10

• Surround renal tubules
• Branch from efferent arteriole
• Designed for absorption and secretion
• Very porous
• Cortical nephrons have only peritubular capillaries

Question 11

What is Vasa Recta?

Answer 11

• Surround only tubules of juxtamedullary
  nephrons
• Branch from efferent arteriole of these nephrons
• Descend deep into the medulla of kidney
• Involved with concentrating urine

Question 12

What are the Steps of Urine Formation?

Answer 12

Steps of urine formation
1. Filtration
* Blood is filtered, filtrate is formed
2. Resorption
* Substances to keep in the body are
returned to blood
3. Secretion
* Substances to be removed from the
body enter into filtrate

Question 13

Nephron Activities during urine production?

Answer 13

Processes that occur within a nephron that are involved in producing urine:
* Filtration
- Movement of fluids/wastes from blood capillaries (glomeruli) into nephron
- Any particles small enough to move through –> non-specific
* Resorption
- Nutrients, water, ions recovered by body; they move from nephron back into peritubular capillaries
- ~99% of original filtrate may be resorbed
* Secretion
- Additional molecules actively and selectively moved from peritubular capillaries into the nephron (to be excreted)

Question 14

What is the purpose of the Renal Corpuscle?

Answer 14

• Site of all filtration
• Made of glomerulus surrounded by glomerular capsule

Question 15

What is the Structure of Renal Corpuscle?

Answer 15

• Glomerulus
• Glomerular capsule

Question 16

What is the Glomerulus?

Answer 16

Glomerulus
* Ball of fenestrated capillaries
* Afferent arteriole leads into glomerulus
* Efferent arteriole leads out of glomerulus

Question 17

What is the Glomerular capsule?

Answer 17

Glomerular capsule
* Two layers
- Parietal layer forms outer layer of capsule
- Visceral layer surrounds capillaries

Question 18

What is the Structure of Renal Corpuscle?

Answer 18

• The visceral layer is made of unusual, branching epithelial cells called podocytes (= foot cells)
• Branches of octopus-like podocytes end in foot processes which interdigitate with each other
• Filtrate passes into capsule space through filtration slits

Question 19

What is the Filtration Membrane?

Answer 19

The filtration membrane consists of
1. Fenestrated epithelium of fenestrated capillary
* Only allows small substances through (no cells)
2. Filtration slits (between foot processes of podocytes)
* Slits are covered with a thin slit diaphragm
3. Basement membrane (fused basal laminae of epithelium and podocyte epithelium)
* Pressure within arterial system pushes small molecules through filtration membrane
* Only the very smallest proteins and small molecules (water, ions, urea, glucose, amino acids) are able to pass through the filtration membrane
- Is called filtrate

Question 20

What is the Proximal Convoluted Tubule?

Answer 20

• Confined to renal cortex
• Made of simple cuboidal epithelium with microvilli
• Lots of microvilli that increase resorption of water, ions, solutes from filtrate
• Resorption & Secretion

Question 21

What is Thin Segment Descending Nephron Loop?

Answer 21

• Resorption and secretion
• Water can leave filtrate by osmosis
• Walls made of simple squamous epithelium

Question 22

What is the Ascending Nephron Loop?

Answer 22

• Resorption and secretion
• Walls made of simple cuboidal epithelium

Question 23

What is the Distal Convoluted Tubule?

Answer 23

• Resorption and secretion (less so than the proximal convoluted tubule)
• Walls made of simple cuboidal epithelium

Question 24

What is the Collecting Duct?

Answer 24

• Several nephrons empty into one collecting duct
• Urine can be concentrated here
• Walls made of simple cuboidal epithelium

Question 25

What are Kidney Stones?

Answer 25

* Can precipitate out of urine —> most commonly from calcium * If they block ureter, urine can collect w/in renal pelvis * Drugs & ultrasound (lithotripsy) most common treatments * HYDRATE —>difficult to form if urine is rich in water

Question 26

What is the Ureter?

Answer 26

* Drains urine from renal pelvis * Lined with transitional epithelium - Able to stretch and recoil (as urine moves through) with help of smooth muscle

Question 27

What is the Urinary Bladder?

Answer 27

* Muscular sac that collects and stores urine

Question 28

What are the components of the Urinary Bladder?

Answer 28

* Detrusor muscle - Under parasympathetic control --> signals contraction when bladder is stretched * Internal urethral sphincter - Smooth muscle - Under sympathetic control --> signal contraction when bladder is filling * External urethral sphincter - Skeletal muscle - Under voluntary control (somatic motor NS)

Question 29

Urethra of the Female

Answer 29

* The urethra drains the urinary bladder * Is made of transitional epithelium close to bladder and changes to stratified squamous as it nears opening to body * 3-4 cm in length (females) * Internal urethral sphincter - Smooth muscle - Keeps urethra closed when urine not passing through * External urethral sphincter - Skeletal muscle; voluntary control

Question 30

Urethra of the Male

Answer 30

* The male urethra is approx. 20 cm in length * Carries both urine and semen * Has different regions - Prostatic urethra -- Length of prostate - Intermediate part of urethra (also called membranous urethra) -- Between spongy and prostatic sections - Spongy urethra -- Length of the penis *Internal urethral sphincter - Smooth muscle, involuntary control * External urethral sphincter - Skeletal muscle, voluntary control * Urinary retention is common in men as the prostate (and potential hypertrophy) press on the urethra