Urinary System Flashcards
What makes up the urinary system?
Upper urinary tract
- Kidneys and ureters
Lower urinary tract
- Bladder and urethra
What are the functions of the kidneys?
Urine formation
- Filter -1200mL of blood/minute
- Regulates levels of fluids and electrolytes
- Removes metabolic wastes, drugs and toxins
Endocrine and metabolic functions
- Erythropoietin: blood cell production
- Renin: blood pressure regulation
- Vitamin D: converts inactive form (cholecalciferol) to active form (calcitriol)
- Gluconeogenesis: formation of glucose from non-carbohydrate sources
What are the structures entering the hilum?
Renal vein
Renal artery
- Accompanied by autonomic nerves and capsular lymphatics
Renal pelvis
- Funnel-shaped beginning of the ureter
Where are the kidneys located?
T12-L3
Lie obliquely in paravertebral gutters
Rt kidney crowned by liver and sits lower than Lt
- Rib 12 overlies upper pole of rt kidney
- Rib 11 overlies upper pole of lt kidney
What is the vertical ROM of the kidneys?
About 2cm (during full respiratory excursion of the diaphragm)
Are the kidneys intra or retro peritoneal?
Retroperitoneal - kidneys lie on the posterior abdominal wall (anterior aspect covered by parietal peritoneum)
What is the gross internal structure of the kidneys?
Cortex
- Beneath capsule
Medulla
Renal pelvis
How is the medulla arranged?
As pyramids (cone-shaped masses) that have papilla and base
Pyramids: striped appearance due parallel bundles of urine collecting tubules
Renal columns: inward extensions of cortical tissue that separate the pyramids
Pyramid + surrounding cortical tissue = kidney lobe
How is the renal pelvis arranged?
Urine drains from papillae of the renal pyramids into several minor calyces
Minor calyces converge to form 2-3 major calyces
Major calyces empty into the renal pelvis
- A funnel-shaped expansion continuous with the ureter leaving the hilum
What are the kidney poles and surfaces?
Lateral border - convex
Medial border - concave, has a vertical cleft (renal hilum) which extends into an internal cavity (renal sinus)
What are the structures entering the hilum anterior to posterior?
Renal vein
Renal artery accompanied by autonomic nerves and apsular lymphatics
Renal pelvis (funnel-shaped beginning of the ureter)
What is the arterial supply of the kidneys?
Renal arteries
What is the venous drainage of the kidneys?
Renal veins
Where do the renal arteries arise from?
Aorta at the level of L1/2 IVD
Which renal artery is longer?
Right renal artery
What happens when each renal artery enters the renal sinus?
Divides into smaller branches
What forms each renal vein?
5-6 interlobar veins that unite at the hilum
Which renal vein is longer than the other?
Left longer than right
What is the nerve supply of the kidneys?
Parasympathetic: CNX vagus
Sympathetic: T10-12 splanchnic nerves
Visceral afferents
What is a nephron?
Basic functional unit of the kidneys
Each kidney has around 1 million nephrons
What is the function of nephrons?
Blood filtration and urine formation
What are the key components of the kidneys microscopically?
Renal corpuscle
- Glomerulus
- Glomerular (Bowman’s) capsule
Renal tubule and collecting duct
- Proximal convoluted tubule
- Nephron loop (loop of henle)
- Distal convoluted tubule
- Collecting duct
What is the glomerulus?
A ‘knot’ of capillaries
receives blood from afferent arteriole and drained by an efferent arteriole
Fenestrations (capillary pores) allow for the easy formation of filtrate
What is the glomerular (bowman’s) capsule?
A cup-shaped hollow structure that surrounds the glomerulus, continuous with the renal tubule
What specialised epithelial cells are found in the glomerular capsule?
Podocytes
- Cling to capillaries
What do foot processes of podocytes contain?
Filtration slits
What is the proximal convoluted tubule?
Receives filtrate from bowman’s capsule
Cuboidal cells lining the wall of PCT possess microvilli and abundant mitochondria
Large capacity for reabsorption of substances
What is the loop of henle?
Descending limb - squamous cells (THIN segment)
Ascending limb - Cuboidal/columnar cells (THICK segment)
What is the distal convoluted tubule?
Cuboidal cells lack microvilli
Conveys urine to the collecting ducts
Where do the collecting ducts receive their filtrate from?
Nephrons
What gives the pyramids their striated appearance?
Collecting ducts
Where is urine delivered?
To the minor calyces via renal papilla
What is the juxtaglomerular apparatus?
A region where the most distal portion of the loop of henle lies against the afferent (and sometimes efferent) arteriole of its glomerulus
What are the 3 types of specialised cells in the juxtaglomerular apparatus?
Macula densa cells
- Wall of tubule, act as chemoreceptors
- Monitor NaCl content of filtrate entering DCT
Juxtaglomerular cells
- Located in the arteriolar walls, act as mechanoreceptors
- Contains granules of renin
Extraglomerular mesangial cells
- Lie in between tubule and arteriole
- Help regulate MD and JG cells
What are the ureters?
Paired, narrow tubes with a thick muscular wall
What do the ureters do?
Convey urine from kidneys to bladder
-1.200ml a day
Where are the ureters located?
Upper half = abdomen
Lower half = pelvis
Where is the abdominal part of the ureters found?
Extends from kidney to bifurcation of common iliac artery
How is urine propelled through the ureters?
Peristaltic contractions of smooth muscle as well as filtration pressure of glomeruli
What is the bladder?
A hollow organ with strong muscular walls
What is the function of the bladder?
Temporary reservoir for urine
- Moderately full: 500ml
- Max capacity: 800-1000ml
What is the location of the bladder?
When empty: within the entire palvic cavity
When distended: domes into abdominal cavity (full bladder may even reach level of umbilicus)
In front of rectum (M) or vagina (F)
What is the location of the male bladder?
Prostate gland: located below the bladder
B/w the posterior surface and rectum: seminal vesicles, vas deferens, rectovesical pouch
What is the location of the female bladder?
in contact with uterus and vagina
Uterovescival pouch: separates bladder from uterus in females (shallow, empty pouch)
