Unit 16 - Urinary System

o   2 kidneys

o   2 ureters

o   1 urinary bladder

o   1 urethra

regulation and elimination

—  wastes e.g. urea, uric acid,

—  hormones

—  drugs (e.g. antibiotics)

—  toxins

—  blood volume

—  blood pressure

—  pH (concentrations of H+ and HCO₃-)

—  concentrations of each ion in the blood (Na+, Ca++, K+, Cl-)

secretion of renal hormones

- retroperitoneal

- right lower than left

- supported and protected by 3 layers of connective tissue

- renal hilus (hilum)

a)      fibrous capsule – outer layer

b)     perirenal fat capsule – middle layer

c)      renal fascia – inner layer

- medial indentation of kidney

- entry point of:

o   renal artery (superior)

o   renal vein (inferior)

o   ureter

o   nerves

o   renal cortex (superficial layer)

o   renal medulla

o   renal pelvis

—  contains parts of nephrons

—  contains afferent and efferent arterioles as well as capillary beds called glomeruli

- renal pyramids (apex of pyramid is called the renal papilla, contain parts of nephrons)

- renal columns (projections of cortex into the medulla, separate pyramids, contains arteries, veins and nerves that supply the cortex)

—  central collecting chamber for filtrate/urine

—  receives filtrate/urine from major calyces

major calyces receive filtrate/urine from minor calyces which are small cup shaped structures that surround the renal papilla

- functional unit of kidney (microscopic)

- two types: cortical, and juxtamedullary

- composed of: renal corpuscle and renal tubules

—  make up majority of nephrons

—  renal corpuscles near kidney surface in cortex

—  short nephron loop that dips into the outer medulla

—  has peritubular capillaries that branch from efferent arteriole and surround DCT and PCT

—  renal corpuscles in cortex near medulla

—  long nephron loops that penetrate deep into medulla (allows for production of dilute or concentrated urine depending on need)

—  has capillaries that branch from efferent arterioles called vasa recta that run parallel to the nephron loop

- in cortex

- site of blood filtration (first step in urine formation), consists of (glomerulus, afferent arteriole, efferent arteriole, glomerular (bowman's) capsule)

- filtration membrane

—  = capillary bed (endothelium formed of simple squamous epithelium)

—  has many fenestrations (pores) between cells

- enters glomerulus

- carries blood delivered to kidney from the renal artery

- exits glomerulus

- drains into peritubular (of cortical nephrons) and vasa recta (of juxtaglomerular nephrons)

- surrounds and collects filtrate (filtered blood plasma) from glomerulus

- 2 layers:

—  Outer layer is a simple squamous epithelium

—  Inner layer is made of cells called podocytes that wrap around glomerular capillaries

- glomerular endothelium (capillaries)

- podocytes (of glomerular capsule)

- shared basement membranes of the two above bullet points

- part of the filtration membrane of renal corpuscles of nephrons which are a microscopic part of the kidneys

- fenestrations (pores) in the simple squamous epithelium allow plasma through, but not formed elements or most large proteins

- part of the filtration membrane of renal corpuscles of nephrons which are a microscopic part of the kidneys

- have many finger-like projections that form a network of filtration slits

- renal tubules are part of the composition of nephrons

- parts: Proximal Convoluted Tubule (PCT)

- Nephron Loop

- Distal Convoluted Tubule (DCT)

- Collecting Ducts

- component of renal tubules which is a component of nephrons

- in cortex

—  receives filtrate from glomerular capsule

—  cells are cuboidal epithelium with dense microvilli

—  reabsorbs most useful substances (e.g. glucose, amino acids) from the filtrate

—  secretes waste products into filtrate

- component of renal tubules which is a component of nephrons

- In the medulla

—  Descending limb (thin) (Simple squamous epithelium, highly water permeable)

—  Ascending limb (thick) (Simple cuboidal  epithelium, water-impermeable)

- component of renal tubules which is a component of nephrons

- in cortex

- cuboidal epithelium

- component of renal tubules which is a component of nephrons

—  in cortex & medulla

—  drain filtrate from numerous nephrons into minor calyces

—  contain cells that regulate water and Na+ reabsorption and acid/base balance of the blood

- regulates the rate of filtrate formation

- point of contact between end of ascending limb, afferent and efferent arterioles at renal corpuscle of same nephron

- Parts: tubular portion (macula densa), vascular (arteriolar) portion

—  modified (tall and narrow) distal convoluted tubule cells

—  monitor filtrate composition

- afferent and efferent arteriolar portion = granular (juxtaglomerular cells)

- modified smooth muscle cells that monitor blood pressure

- secrete an enzyme/hormone that helps to regulate blood pressure and ion balance

—  transports urine from renal pelvis to bladder

—  retroperitoneal

- Mucosa: transitional epithelium (stretches)

- Muscularis externa: smooth muscle

- Adventitia: connects ureter to body wall

—  short term storage of urine

—  retroperitoneal

the space behind the abdominal cavity and in front of the lower back

- Mucosa: transitional epithelium with rugae

- Muscularis externa: is detrusor muscle - smooth muscle, contraction of detrusor muscle causes urination

- Adventitia/Serosa (mostly adventitia, serosa covers the superior surface)

- drains urine from the bladder

- transports urine and when testes are present, also transports semen

- 2 sphincters (both surround proximal end of urethra)

- Mucosa – transitions from transitional epithelium to stratified squamous epithelium

- Muscularis externa – is smooth muscle

- Adventitia only

- internal urethral sphincter (smooth muscle): thickening of detrusor muscle at base of bladder

- external urethral sphincter (skeletal muscle), in urogenital diaphragm

bacterial infection of the mucosa of the bladder and/or urethra (most common). Can also involve ureters and kidneys (less common).

inflammation of the glomeruli and structures of the filtration membrane that impairs their ability to filter blood plasma