Histology Of Urinary System

Front 1

what is the main function of the urinary system [5]

Back 1

1. conserve H20, produce & excrete urine

2. Regulate blood volume & body fluids
[Regulate Na+,K+,Ca2+,HPO42-,Cl-]
[Regulate blood pH: excrete H+, conserve HCO3-]

3. Secrete erythropoietin for erythropoiesis

4. 1,25-hydroxycholecalciferol: synthesize vit D & Ca2+ metabolism

5. Renin secretion for angiotensin I, cleaving angiotensinogen & BP regulation

Front 2

what to observe in urine production/secretion? [4]

Back 2

1. volume (normal 1.25 l/day with 75% water)
• polyuria, oligouria, incontinence, retention

2. Colour

3. Clarity (levels of cells, proteins, crystal/salt)

4. Smell/odour
• urea breakdown
• sweet & fruity (diabetes, ketones)
• unpleasant (bacterial infection)
• maple syrup (metabolic disorder)

Front 3

clinical conditions of urinary system (5)

Back 3

1. PCKD
2. UTI, kidney infections
3. Frequent micturition (aged patients)
4. DM: hyperglycemia, polyruria, polydipsia
5. Diabetes insipidus:
• lack of ADH or response → lose ability to reabsorb water from DCT & CD, leading to large volume of urine production (up to 22 l/day)
• excessive thirst/excrete much severely diluted urine

Front 4

Morphology of PCT (7)

Back 4

• simple cuboidal epithelium
• apical (faces filtrate) surface: many microvilli (luminal brush border)
• basal (faces interstitial fluid) interdigitations
• lateral surface between cells
• strongly eosinophilic cytoplasma
• no distinctive cell border
• substances pass through cell wall

Front 5

1. function of PCT (2)

2. how is this changed in DM? (2)

Back 5

1.
• Na+ & substances (amino acid, proteins & sugars) are removed.
• Water follows passively

2.
• conc. of glucose in filtrate exceeds rate of transport
• high conc. of glucose in plasma, thus filtrate, reflected in glucose in urine

Front 6

describe the histology of loop of Henle

Back 6

• initial part of desc. limb: simple cuboidal epithelium
• latter part: simple squamous epithelium
• initial part of asc. limb: simple squamous epithelium
• distal part: simple cuboidal epithelium

Front 7

function of loop of Henle

Back 7

descending thin segment
• highly permeable to water: water moves into interstitial fluid then vasa recta
• moderately permeable to urea, sodium, other ions

ascending thin segment
• not permeable to water
• permeable to solutes. solutes diffuse out into more diluted interstitial fluid as ascending limb projects toward cortex

Front 8

describe the histology of distal convoluted tubule (4)

Back 8

• simple, pale stain cuboidal epithelial cells,
• appear less in one section since shorter
• few microvilli, less brush border on luminal surface, more distinctive border
• smaller cell size

Front 9

what are the common features between PCT and DCT (3)

Back 9

• found in cortex
• basolateral membrane interdigitation
• numerous mitochondria

Front 10

what is differential features between PCT and DCT (8)

Back 10

• PCT thicker wall, DCT thinner wall
• PCT smaller lumen, DCT larger lumen
• PCT numerous microvilli, DCT no brush border
• PCT indistinct cell boundary, DCT distinct cell boundary
• PCT acidophilic cytoplasma, DCT less acidophilic
• PCT fewer nuclei/XS, DCT more nuclei/XS
• DCT stain darker than PCT

Front 11

describe function of DCT (5)

Back 11

response to renin/angiotensin/aldosterone
• aldosterone fits into aldosterone receptor in DCT (which is behind basal & apical membrane)
• ↑ synthesis of transport protein
• countertransport of Na+ and H+
• active transport of Na+ and K+
• Cl- reabsorbed

Front 12

morphology of collecting tubule (4)

Back 12

• similar to DCT, with larger lumen
• found in cortex, medulla, w. many in medullary rays
• cells pale staining cytoplasm
• tubules join to collecting ducts

Front 13

what is the function of medullary CT? (3)

Back 13

• ↑permeability of CT to water in response to ADH [which is synthesized by hypothalamus & released by posterior lobe of pituitary]
• if ADH absent, water not reabsorbed. Urine is dilute
• if ADH present, water moves OUT. Urine is conc.

Front 14

describe histo (3) and function (1) of collecting duct

Back 14

• Large diameter w. simple pale staining cuboidal epithelium
• CD forms from many distal tubules
• form medullary rays & lead to papillary ducts (ducts of Bellini)

• reabsorb water

Front 15

transitional epithelium:
• structure
• function

Back 15

• S: epithelial cells change shape depending on amount of distention of organ
• F: accommodates fluctuations in volume of fluid in tube; protects against hypertonic urine

Front 16

describe urine movement (4)

Back 16

• hydrostatic pressure forces urine through nephron
• peristalsis moves urine through ureters from renal pelvis to urinary bladder (from every few secs, to every 2-3 min)
• PSNS ↑ frequency of peristalsis, SNS ↓ frequency
• ureters enter bladder obliquely through trigone: pressure in bladder compresses ureter, preventing backflow

Front 17

contrast male and female bladder/urethra (4)

Back 17

Female:
• 4 cm
• opens into vestibule ant. to vaginal openine

Male
• 11cm
• extends from inferior part of urinary bladder through penis

Front 18

histology of female urethra (3)

Back 18

• pseudostratified columnar epithelium
• muscular walled tube w. transitional ep. near bladder
• non-keratinized strat. squamous epithelium close to skin

Front 19

histology of male urethra (4)

Back 19

urinary & reproductive function
• prostatic (transitional)
• membraneous & cavernous (spongy)
• penile (pseudo or stratified columnar epi)
• non-keratinized strat. squamous epithelium in spongy urethra

Front 20

structure (2) and function (4) of inferior urethra

Back 20

structure: (multiple layers of cells)
• cuboidal in basal layer,
• progressively flattening towards surface (nucleus & cytoplasm still rained)

Functions
• protect against abrasion
• protect vs caustic (silver nitrate, H2SO4) chemicals
• protect vs water loss
• protect vs infection

Front 21

3 major cell types present in the JG apparatus, and outline the functions of each of these cell types

Back 21

JG cells:
- secrets renin which converts angiotensinogen (circulating in the plasma) to angiotensin I then cleave to form angiotensin II by angiotensin converting enzyme (ACE)

Macula densa cells: Modified DCT cells
- sensitive to osmolarity & volume of filtrate
- regulates GFR [increase NaCl uptake → increase ATP to adenosine → increase vasoconstriction → GFR increase]
- Detects the GFR & secretes prostaglandins which act on their receptors on the juxtaglomerular cells to regulate the renin secretion from the JG cells

Lacis cells:
- like mesangial cells with gap junction among them and juxtaglomerular cells → functional link between these cells