Liver and Kidney

Question 1

Liver

Answer 1

• largest organ, largest mass of glandular tissue in body.
• plays an important role in the uptake, storage and distribution of nutrients
• produces the majority of circulating plasma proteins (e.g. albumins), stores iron, converts vitamins and degrades drugs and toxins
• acts as an exocrine organ (produces bile) and performs endocrine-like functions.
• remarkable capacity for regeneration after either surgical removal or after chemical injury, 51% of the original liver can regenerate back to its full size.

Question 2

Dual blood supply in the liver

Answer 2

• a venous supply via the hepatic portal vein

- an arterial supply via the hepatic artery.

Question 3

Structural components of the liver

Answer 3

• parenchyma (P) (plates of hepatocytes)
• connective tissue stroma (CT)
• sinusoidal capillaries (hepatic sinusoids)
• perisinusoidal spaces (of Disse).

Question 4

Unit structure of the liver

Answer 4

• classic lobule (polygonal shape)
• portal lobule (triangular in shape)
• liver acinus (a diamond-shaped area that has three zones and best correlates to blood perfusion, metabolic activity and liver pathology)

Question 5

Classical lobule

Answer 5

• the unit drained by a central vein

Question 6

Portal lobule

Answer 6

• the unit supplied and drained by portal triad

Question 7

Liver acinus

Answer 7

• the unit supplied and drained by terminal branches of portal triad vessels

Question 8

Hepatocytes in classic lobule

Answer 8

• organized into irregular anastomosing plates that radiate towards a central vein

Question 9

Portal triad

Answer 9

• occupy corners of polygonal classic tobule

- contains branches of portal vein (PV), hepatic artery, (HA), bile ducts (BD) and small lymphatic vessels

Question 10

Hepatocytes

Answer 10

• constitute 80% of the liver and are large, polygonal cells with spherical nuclei (often binucleated) and acidophilic cytoplasm containing sER, rER, numerous mitochondria, peroxisomes and multiple small Golgi complexes
• basal surface has contact with the perisinusoidal space (of Disse), whereas the apical surface is connected to the adjacent hepatocyte to form a bile canaliculus.

Question 11

Bile flow

Answer 11

• Bile canaliculi drain into the short canals of Hering, which are partially lined with hepatocytes and cuboidal cholangiocytes (cells lining the biliary tree)
• Canals of Hering harbour specific hepatic stem cells
• Flow of bile: bile canaliculi → canals of Hering → intrahepatic bile ductule → interlobular bile ducts (which is port of the portal triad) → right and left hepatic ducts → common hepatic duct → gallbladder → bile duct → duodenum

Question 12

Hepatic sinusoids

Answer 12

• sinusoids form irregular vascular channels that run parallel and between the plates of hepatocytes
• receive mixed blood (~75%) from venous portal circulation and arterial blood (~25%) from systemic circulation.

Question 13

Discontinuous sinusoidal endothelium

Answer 13

• large fenestrae, large gaps between neighbouring endothelial cells
• Blood cells are unable to pass through fenestrae and gaps, fluid and protein can pass

Question 14

(Perisinusoidal) Space of Disse

Answer 14

• lies between hepatocytes and the endothelium

- site of exchange of materials between blood and liver cells

Question 15

Kupffer cells

Answer 15

• aka stellate sinusoidal macrophages

- remove senile red blood cells and recycle iron molecules

Question 16

Hepatic stellate cells

Answer 16

• reside in the perisinusoidal spaces and are loaded with lipid droplets for storage of vitamin A
• In pathologic conditions, Ito cells have the potential to differentiate into myofibroblasts (go from quiescent to activated state).

Question 17

Causes of cirrhosis

Answer 17

• most common: alcohol,hepatitis B,hepatitis C andnon-alcoholic fatty liver disease
• less common: autoimmune hepatitis,primary biliary cholangitis,haemochromatosis, certain medications andgallstones.

Question 18

Cirrhosis

Answer 18

• Healthy liver cells are slowly replaced by scar tissue
• progressive disease which can take years to develop due to long-term damage
• Can develop into liver failure were the liver has lost too many hepatocytes and is no longer to coupe with the demand
• 2 hallmarks: Thick bands of mature fibrous tissue (fibrosis) + nodules of ‘regenerative’ hepatocytes

Question 19

Hepatocellular carcinoma

Answer 19

• mostly occurs in people withcirrhosis of the liver, and so risk factors generally include factors which cause chronic liver disease that may lead to cirrhosis
• liver is most frequent site of secondary tumours (most noticeably from GIT).
• Surgical resection (only 5-15% of patients are suitable), liver transplantation (need donor and immunosuppressive medication)

Question 20

Obstructive jaundice (or icterus)

Answer 20

• Due to narrowed or blocked bile/pancreatic duct, preventing normal drainage of bile from the bloodstream into the intestines
• Bile accumulation in bile duct (can progress and induce necrosis of hepatocytes in portal areas)

Question 21

Liver diseases

Answer 21

• Alcohol-related liver disease
• Non-alcoholic fatty liver disease
• Infection (Tuberculosis, Spirochaetes)
• Haemochromatosis

Question 22

Laboratory investigations

Answer 22

• Liver Function Tests (LFT’s) (biochemistry)
• Biopsy - special stains: Ferric Iron (haemosiderin), Retic (reticulin fibres), Van Gieson (collagen, bile), PAS/D.PAS (glycogen)

Question 23

Role of the kidney

Answer 23

• eliminate waste products
• maintain normal acid-base balance
• conserve fluid, electrolytes and other essential substances

Question 24

Structure of the kidney

Answer 24

• Capsule: dense irregular collagenous connective tissue, plus occasional fibroblasts and blood vessels
• Cortex: parts of nephrons: collecting tubules (arranged in cortical labyrinths) and medullary rays; blood vessels; connective tissue
• Medulla: renal pyramids containing part of nephron
• Pelvis: beginning of main excretory duct

Question 25

External anatomy of kidney

Answer 25

• retroperitoneal
• bean‑shaped, hilum faces medially
• renal artery, renal vein, ureter in renal sinus
• calyces
• medulla

Question 26

Internal morphology of kidney

Answer 26

• kidney capsule
• cortex: medullary rays
• medulla: renal pyramid, renal column, renal papilla, minor calyx, major calyx
• renal pelvis

Question 27

Renal Corpuscle (Glomerulus, Bowman’s capsule)

Answer 27

• afferent and efferent arterioles
• juxtaglomerular apparatus
• glomerulus
• fenestration (pore)
• proximal convoluted tubule
• glomerular capillary
• podocyte
• filtration slit
• bowman’s capsule
• distal convoluted tubule

Question 28

Nephron

Answer 28

• Proximal convoluted tubule: active reabsorption
• Loop of Henle: descending, ascending
• Distal convoluted tubule
• Juxtaglomerular apparatus /Macula densa: renin production (blood pressure control, influences rate of renal blood flow)
• Glomerulus: (filtration unit) (250 µm) - afferent/efferent arterioles, Bowman’s capsule, Podocytes

Question 29

Urine drainage

Answer 29

• renal corpuscle
• proximal convoluted tubule
• thick descending limb
• thin loop (of Henle)
• thick ascending limb
• distal convoluted tubule
• cortical collecting tubules
• medullary collecting ducts
• papillary collecting ducts (of Bellini) ‑ area cribrosa
• renal papilla

Question 30

Proximal convoluted tubule (& thick descending tubule)

Answer 30

• simple cuboidal epithelium
• intensely eosinophilic
• prominent brush border - narrow lumen
• numerous lateral folds & basal striations

Question 31

Thin loop of Henle

Answer 31

• simple squamous epithelium
• nuclei bulge into the lumen
• highly permeable to water, urea, ions

Question 32

Distal convoluted tubule (thick descending tubule)

Answer 32

• simple cuboidal epithelium
• weakly eosinophilic
• low brush border ‑ wide lumen
• impermeable to water / urea

Question 33

Collecting tubules/ducts

Answer 33

• simple cuboidal epithelium
• pale cytoplasm
• prominent lateral cell boundaries
• luminal (apical) surface may be scalloped

Question 34

Juxtaglomerular cells

Answer 34

• Secrete renin in response to low blood pressure or low blood sodium

Question 35

Macula densa

Answer 35

-Senses decreased salt concentration in the filtrate and signals juxtaglomerular cells to release renin

Question 36

Arterial supply in kidneys

Answer 36

• Renal artery
• Segmental arteries
• Lobar arteries
• Interlobar arteries
• Arcuate artery (corticomedullary junction)
• Interlobular arteries
• Afferent arterioles
• Glomerular capillaries
• Efferent arterioles

Question 37

Venous drainage

Answer 37

• stellate veins
• interlobular veins
• arcuate veins

Question 38

Clinical issues of kidney

Answer 38

• Nephritis
• Acute glomerulonephritis
• Congenital (polycystic)
• Tumours

Question 39

Laboratory investigations

Answer 39

• Biopsy:
• Electron Microscopy
• Immunofluorescence
• IgA, M, G, Fibrinogen, C3, C4
• Paraffin wax
• special stains:
• PAS (basement membrane)
• PA Silver (basement membrane + spikes)
• MSB - connective tissue, fibrin
• Sirius/Congo Red - amyloid