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USMLE

Cell Bio/Histo/Path -2

QuestionAnswer
True or False: Collagen is the most abundant protein in the body? True. (25% of all protein in the human body is collagen)
Collagen types and their primary locations Be (So Totally) Cool, Read Books 1. (90% of all collagen) Bone, Skin, Tendon (bONE) 2. Cartilage (carTWOlage) 3. (Reticulin)-blood vessels 4. Basement membrane
Collagen Type I locations Be (So Totally) cool, read books -Bone (bONE) -Skin -Tendon -dentin -fascia -cornea -late wound repair
Collagen Type II locations be (so totally) COOL, read books -Cartilage (carTWOlage) -vitreous body -nucleus pulposus
Collagen Type III locations be (so totally) cool, READ books (Reticulin) -blood vessels -skin -uterus -fetal tissue -granulation tissue
Collagen Type IV locations be (so totally) cool, read BOOKS -basement membrane or basal lamina (four under the floor)
Collagen synthesis: list of events and locations Intracellular 1. Synthesis (Rough Endoplasmic Reticulum) 2. Hydroxylation (Endoplasmic Reticulum) 3. Glycosylation (Golgi) 4. Exocytosis Extracellular 5. Proteolytic processing 6. Cross-linking
Collagen production step 1: Synthesis -In rough endoplasmic reticulum -translation of collagen alpha chains (aka preprocollagen)
Composition and other name of collagen alpha-chains -Gly-X-Y (where X and Y are proline, hydroxyproline, or hydroxylysine) -aka preprocollagen
Composition and other name of preprocollagen -Gly-X-Y (where X and Y are proline, hydroxyproline, or hydroxylysine) -aka collagen alpha-chains
Collagen production step 2: Hydroxylation -In endoplasmic reticulum -Hydroxylation of specific proline and lysine residues (using vitamin C)
Collagen production step for which vitamin C is required Hydroxylation of Gly-X-Y chains to form hydroxyproline or hydroxylysine
Collagen production step 3: Glycosylation -In Golgi apparatus -Glycosylation of preprocollagen lysine residues and formation of procollagen (triple helix of three collagen alpha chains)
Composition of procollagen Triple helix of three collagen alpha chains (aka three preprocollagen chains)
Osteogenesis Imperfecta: Pathophysiology Cannot take glycosylated alpha-chains and form procollagen (triple helix)
Collagen production step 4: Exocytosis Exocytosis of procollagen
Collagen production step 5: Proteolytic processing Cleavage of terminal regions of procollagen, transforming it into insoluble tropocollagen
Composition of tropocollagen Procollagen (triple-helix) with terminal regions cleaved
Collagen production step 6: Cross-linking Reinforcement of many staggered tropocollagen molecules by covalent lysine-hydroxylysine cross-linkage to make collagen fibrils
Enzyme which performs collagen cross-linking (final step) Lysyl oxidase
Ehlers-Danlos syndrome: Pathophysiology Nonfunctioning lysyl oxidase resulting in lack of collagen fibrils (linked tropocollagen molecules)
Ehlers-Danlos syndrome: Presentation -Hyperextensible skin -Tendency to bleed/easy bruising -Hypermobile joints
Ehlers-Danlos syndrome: of types
Ehlers-Danlos syndrome: Inheritance Varies
Ehlers-Danlos syndrome: Most frequently affected collagen type and result Type III collagen resulting in blood vessel instability
Osteogenesis Imperfecta: Types -Abnormal collagen type I (bONE) --Most common --Autosomal-dominant -Type II --Fatal in utero or neonatal period
Osteogenesis Imperfecta: Presentation 1. Brittle bone disease: Multiple fractures with minimal trauma (often during birth) 2. Blue sclearae (due to translucency of connective tissue over the choroid) 3. Hearing loss (abnormal middle ear bones) 4. Dental imperfections due to lack of d
Multiple fractures in a child: Differential Diagnosis -Child abuse -Osteogenesis Imperfecta
Osteogenesis Imperfecta: Incidence 1:10,000
Immunohistochemical stain for: Connective tissue Vimentin
Immunohistochemical stain for: Muscle Desmin
Immunohistochemical stain for: Epithelial cells Cytokeratin
Immunohistochemical stain for: Neuroglia GFAP (Glial fibrillary acid proteins)
Immunohistochemical stain for: Neurons Neurofilaments
Vimentin stains for: Connective tissue
Desmin stains for: Muscle
Cytokeratin stains for: Epithelial cells
GFAP (Glial fibrillary acid proteins) stains for: Neuroglia
Neurofilaments stain for: Neurons
Elastin: Description and Location Stretchy protein within lungs, large arteries, elastic ligaments
Elastin and Collagen: Peptide composition difference Both: Proline and lysine rich Collagen: Hydroxylated forms Elastin: Non-hydroxylated forms
Elastin: Structure Tropoelastin with fibrillin scaffolding (fibrillin defect in Marfan's syndrome)
Elastin: Conformations Relaxed and stretched
Elastase: function Break down elastin
Elastase inhibitor alpha-1-antitrypsin
Elastase excess: Found where Found in emphysema
Association of emphysema with elastase Excess elastase activity can cause emphysema
Apoptosis: Characteristics 1. Cell shrinkage 2. Chromatin condensation 3. Membrane blebbing 4. Formation of apoptotic bodies which are then phagocytosed
Apoptosis: Events which initiate it -Embryogenesis -Hormone induction (menstruation) -Immune cell-mediated death -Injurious stimuli (eg radiation, hypoxia) -Atrophy
Necrosis: Definition Enzymatic degradation of a cell resulting from exogenous injury
Necrosis: Characteristics 1. Enzymatic digestion 2. Protein denaturation 3. Release of intracellular components 4. Inflammatory process.
Necrosis: Types and where they are found 1. Coagulative (heart, liver, kidney) 2. Liquefactive (brain) 3. Caseous (Tuberculosis) 4. Fat (Pancreas) 5. Fibrinoid (blood vessels) 6. Gangrenous (limbs, GI tract)
Reversible or irreversible cell injury: Cellular swelling Reversible
Reversible or irreversible cell injury: Nuclear chromatin clumping Reversible
Reversible or irreversible cell injury: Decreased ATP synthesis Reversible
Reversible or irreversible cell injury: Ribosomal detachment Reversible
Reversible or irreversible cell injury: Glycogen depletion Reversible
Reversible or irreversible cell injury: Plasma membrane damage Irreversible
Reversible or irreversible cell injury: Lysosomal rupture Irreversible
Reversible or irreversible cell injury: Calcium influx leading to oxidative phosphorylation Irreversible
Reversible or irreversible cell injury: Nuclear pyknosis Irreversible
Reversible or irreversible cell injury: Karyolysis Irreversible
Reversible or irreversible cell injury: Karyorrhexis Irreversible
Reversible or irreversible cell injury: Mitochondrial permeability Irreversible
Created by: Asclepius