Another Hard Day at the Office

Anatomy

100

What marks the junction between the foregut and the midgut?

• inferior edge of the major duodenal papilla

200

Outline blood supply of the liver

• hepatic artery supplies oxygenated blood
• portal vein supplies nutrient and antigen rich blood from GIT 
• blood mixes in sinusoids which are specialised fenestrated capillaries 
• drains into central vein in centribolar region (zone 3)

300

What are stellate cells and their function?

• perisinusoidal cells that store vitamin A and manage extracellular matrix remodelling
• in liver injury they activate myofibroblasts --> fibrosis, inflammation, growth factor 

400

Describe the structure of the exocrine pancreas

• series of tubuloacinar glands 
• lobules with secretory units called acini (simple columnar)
• apical cytoplasm contains secretory vesicles with zymogens/pro-enzymes 
• ducts extend from centre of acinus (simple cuboidal to columnar)

500

Compare and contrast anatomical features of jejunum and ileum:

- lumen

- walls

- plicae circulares

- vascularity

- mesentery 

jejunum (function is chemical digestion and absorption)

• larger lumen 
• thick and heavy walls
• lots of plicae circulares 
• greater vascularity 
• less fat in mesentary 
• long vasa recta
• few large arcades 

ileum (function is detection of infection)

• smaller lumen
• thin and light walls
• peyer's patches
• few plicae circulares
• less vascularity
• more fat in mesentary
• short vasa recta 
• many small arcades

Physiology

100

What are the three stages of swallowing?

• oral/buccal
• pharyngeal
• esophageal

200

Outline homeostatic feedback loop when you get dehydrated

• in dehydration, ECF volume decreases which results in an increase in sodium concentration 
• two things are detected: 
  • change in vascular volume (baroreceptors)
  • change in plasma osmolarity (osmoreceptors)
• activation of SNS and RAAS: 
  • increase thirst 
  • renal conservation 
  • reduced Na excretion 
• ECF volume restored: ADH, renin, aldosterone return to baseline

300

Outline the relative volumes in the body fluid compartments

• females: 55% water, 45% solid
• males: 60% water, 40% solid

60% of total fluid:

• 2/3 intracellular fluid (inside cells)
• 1/3 extracellular fluid: 80% interstitial fluid (between cells), 20% plasma (inside blood vessels)

400

Outline the flow of bile from hepatocytes to the duodenum 

• hepatocytes produce bile --> canaliculi --> portal triad --> hepatic ducts --> porta hepatits --> common hepatic duct --> cystic duct --> gall bladder 
• gall bladder --> cystic duct --> common bile duct --> hepatopancreatic ampula --> major duodenal papilla --> duodenum 

500

Describe stages of lipid absorption

• at brush border: monoglycerides and free fatty acids leave micelles and passively diffuse through cell membrane 
• Inside cells: monoglycerides and free fatty acids resynthesised into triglycerides 
• Triglycerides aggregate + covered with lipoprotein to form chylomicrons -> leave basal membrane by exocytosis 
• Transport around the body: 
  • Chylomicrons enter lacteals (lymphatic vessels) 
  • Fatty acids enter blood stream 
• Stored in adipocytes and muscle cells

Pathophysiology

100

What are gallstones made of?

constituents of bile:

- cholesterol

- bilirubin

- calcium salts

200

Describe the distribution of GIT involvement in crohn's disease

• 80% have small intestine  (usually ileum)
• 50% have ileum and colon (ileocolitis)
• 30% have only distal ileum (ileitis)
• 20% have colon (half of which have sparing of colon)
• small % have involvement of upper GIT (mouth, esophagus, stomach, duo)

300

Outline the pathophysiology of autoimmune gastritis

1. autoimmune reaction to parietal cells or intrinsic factor
2. results in production of autoantibodies against parietal cells or intrinsic factor
3. loss of parietal cells 
4. reduced production of HCl (hypochlorhydria) 
5. reduced absorption of B12 --> pernicious anemia, also interferes with erythropoiesis in bone marrow 

400

Outline how biliary obstruction leads to conjugated hyperbilirubinemia 

- biliary obstruction blocks the flow of bile (cholestasis) from entering duodenum

- conjugated bilirubin backs up in liver leading to increased pressure inside bile ducts and hepatocytes

- increased pressure increases permeability of bile ducts/hepatocytes --> accumulated conjugated bilirubin refluxes into sinusoidal blood (plasma)

- results in high levels of conjugated bilirubin in blood

- clinical signs: dark urine, jaundice, pale stools

500

Describe the four different types of hypersensitivity reactions. Provide an example of each.

Type I: IgE-mediated

- allergen binds to IgE on mast cells --> degranulation 

- e.g. hay fever, food allergies

Type II: IgG-mediated cytotoxic 

- activation of complement of cytotoxic T cells 

- e.g. transfusion reactions 

Type III: Immune complex-mediated 

- antigen-antibody complex deposited into tissues 

- causes activation of neutrophils to site

- e.g. SLE, rheumatoid arthritis, glomerulonephritis 

Type IV: delayed 

- Th1 cells secrete cytokines which activate macrophages and cytotoxic T cells

- e.g. celiac disease, crohn's disease, contact dermatitis, tuberculin reaction, DM, rheumatoid arthritis

Clinical

100

What is the significance of the tertiary branching of the liver forming eight segments?

each segment is functionally independent from each other
surgically independent due to blood supply
damage in one segment can be cut off without interupting function of other

200

What are medications used to treat heart failure with reduced ejection fraction?

BAND IS SAD

• Beta blockers
• ACE inhibitors
• Neprilysin inhibitors 
• Diuretics  
• Ivabradine 
• Spironolactone
• SGLT2 inhibitors 
• Angiotensin II receptor antagonists 
• Digoxin (particularly if atrial fibrillation) 

300

List four differential diagnoses for diarrhea

• infection: giardia, e coli, salmonella, hep a
• IBD: crohn's, ulcerative colitis
• functional gut disorders
• celiac disease
• female specific: endo, pregnancy
• hyperthyroidism 
• psychological: anxiety
• laxatives

400

What happens to volume of the body fluid compartments when you bleed?

• blood loss results in reduction in blood pressure
• compensatory fluids shifts from interstitial fluid into vascular system
• takes 15 mins for starling forces to kick in, 1-2 hours to see change in haematocrit 
• compensation results in increase plasma volume, haemodilutio (due to more water in blood), reduced Hb and reduce haematocrit 

500

Read the following case study. Determine the cause of fluid loss, what fluid compartment is affected and how you would assess and treat the patient.

• total body loss due to sweating from heat and blunted thirst response due to drugs 
• compartment is ECF, particular Na and Cl loss 
• assessment: UEC, plasma osmolality, Hb and haematocrit 
• treatment: fluid resus with crystalloid solution
  • molecules cross capillary walls into interstitial fluid

Spiral Learning

100

Where does cervical cancer typically occur?

• in transformation zone 
• involves metaplastic changes in transformation zone which produces precancerous lesions

200

How does pregnancy cause heartburn?

• progesterone causes smooth muscle relaxation --> reduced gastric motility --> reduced lower esophageal sphincter tone --> regurgitation of gastric acid into esophagus
• increased intragastric pressure due to fetus pushing up

300

What are some consequences of premature births

• neurological underdevelopment
• CVS - patent ductus arteriosus
• increased infection risk due to lower level of maternal AB and innate immune response
• thermoregulatory challenges - hypothermia risk to due to limited fat stores and immature skin 
• sensory organ risks - retinopathy and hearing impairments

400

Compare and contrast the microscopic features of benign vs malignant neoplasms

• architecture
• basement membrane
• cytology
• mitoses
• vascular invasion 

Benign:

- architecture resembles normal tissue

- limited by basement membrane

- cytologically resemble normal cells

- mitoses uncommon

- no vascular invasion 

Malignant:

- loss of normal architecture and epithelial polarity

- defective basement membrane/invasion

- features of anaplasia: pleomorphism, prominent nucleoli, giant cells, hyperchromasia

- mitoses

- invasion of lymphatics and blood vessels

500

Describe hormone levels across menstrual cycle

• Declining estrogen and progesterone levels just before menses STOPS inhibition of hypothalamic GnRH pulses --> increase in FSH
• increase in FSH triggers recruitment of a new wave of ovarian follicles for maturation
• Low-levels of estrogen at the beginning of the follicular phase inhibit HP axis (and therefore recruitment of additional follicles), but promote follicular maturation and estrogen production
• High-level estrogen just prior to ovulation stimulates GnRH and LH release
• GnRH stimulates an LH surge, as well as FSH release, from the anterior pituitary.  
• LH surge triggers final follicle maturation and ovulation.
• Corpus luteum that forms from the ruptured ovarian follicle following ovulation produces progesterone and estrogen, which inhibit hypothalamic and pituitary hormones