Cluster Abdomen has a challenging written exam in which a number of themes are covered including physiology, medical microbiology, molecular cell biology and radiology.
In this document all the lectures from these different themes are summarised with all the detail needed to pass the exam.
From a...
Physiology - Overview
- Male Hormones
- Testosterone
- High testosterone -> hair loss on head, hair growth in pubic region, chest
- More FGF stimulation
- DHT (dihydrotestosterone)
- Definition: main androgen
- Formation
- 2 5 alpha reductase: found in stromal cells
- 1 5 alpha reductase: found in peripheral organs (liver, skin)
- Function:
- Bind to nuclear androgen receptor in stromal/epithelial prostate
cells
- Higher affinity than testosterone
- Stimulates transcription of androgen-dependent genes (ie. GFs)
- FGF, TGF b
- FGFs: produced by stromal cells, paracrine regulator androgen-
stimulated epithelial development in embryonic and adulthood
prostatic development
- TGF-b: produced by peripheral organs ; mitogen for fibroblasts,
mesenchymal cells ; inhibits epithelial proliferation
- Celiac Disease
- Protein
digestion
- Oligo
peptides: broken down brush border peptidases
, - Peptides: enter enterocytes via secondary active transport with H+ with a
transmembrane protein
- Amino acid: enter enterocytes via secondary active transport with Na+ or via
facilitated diffusion
- Cytoplasm: cytosolic peptidases with break down remaining peptides
- Diarrhea
- Types
- Osmotic
- Higher osmotic concentration in feces than in serum
- More fluid drawn into colon than reabsorptive capacity
- Linked to malabsorption
- Lactose intolerance
- Gluten intolerance
- Steatorrhea
- Motility
- Stimulated parasympathetically ; inhibited sympathetically
- Segmentation and peristalsis
- Migrating motor complex initiates peristaltic waves of 2ft/90mins in
small intestine
- Regulated by motilin
- Haustral contraction in the colon occur every 30 min
- Slow motility allows for sufficient absorption
- Secretory
- Bloody/inflammatory
- Smooth muscle contraction
- Characteristics: no striations, no orderly sarcomeres, negligible amounts of
troponin, lots of actin compared to myosin
- Thin filaments anchored to dense bodies attached to next filament
network
- Membranes of adjacent cells have gap junctions -> nexus for action
potential = synchronous contraction
- Contraction
- Pacemaker cell -> action potential -> nexus -> smooth muscle
, - In resting muscles: low intracellular Ca2+ and actin and myosin do not
interact
- Phasic: AP opens voltage dependent Ca2+ channels -> influx of Ca2+
down gradient
- Ca2+ binds to calmodulin -> kinase activation on light chain, and
myosin in thick filament -> catalyses phosphorylation of myosin of
myosin (via dephosphorylation of ATP) -> phosphorylated myosin
binds to actin -> ATP split to move across bridges, myofilaments
slide past each other => contraction
- Myosin deactivated by dephosphorylation = ADP phosphorylated
back to ATP
- Acute pancreatitis
- Autodigestion of pancreatic organ by inappropriately activated pancreatic
enzymes
- Activation of trypsin by 3 pathways
, The
GI
Tract
Celiac Disease
1. Definition
- Definition: gluten sensitive enteropathy and nontropical sprue
- Proximal to distal distribution: severity diminishes distally reflecting exposure of
intestinal mucosa to dietary gluten
- Epidemiology
- 1/113 in the US ; increased incidence over 50 years
- Most patients have atypical presentations
- Etiology
- Immune disorder: triggered by environmental agent (gliadin component of gluten)
in genetically predisposed individuals
- Genetic factors: HLA-DQ2 gene loci
- Contributes to > ⅓ of the disease
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