HMB302 Lab Notes

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School

University of Toronto *

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Course

302

Subject

Medicine

Date

Oct 30, 2023

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pdf

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Uploaded by DrCrane3711

Lecture 1: Epithelial Tissue Simple Epithelium - Single layer Simple Squamous - Single layer of cells - Width and depth is greater than height - Low profile polygonal cells, cytoplasm is too thin to be visible histologically - Nucleus may bulge towards the surface - Locations : blood and lymphatic vessels, lung alveoli, peritoneal, pleural, and pericardial cavities, kidney: loop of Henle and Bowman’s capsule Simple Cuboidal - Single layer of cuboidal cells - Height = width = depth - “Cube” shape with a centrally placed nucleus - Found in ducts of many glands as it helps with secretion, absorption, and protection - Locations : surface of the ovary, capsule of the lens, lining the collection tubules of the kidney, ducts draining exocrine glands Simple Columnar - Height is greater than depth and width - Surface view → similar to cuboidal - Longitudinal section → tall, rectangular cells with an oval nucleus at the basal part of the cell - Helps with transportation, absorption, secretion, and protection - Can have microvilli or be ciliated or non-ciliated - Non-ciliated locations: gall bladder, salivary glands

- Microvilli or ciliated locations: lining the digestive system, uterus, oviducts, small bronchi, ductuli efferentes of testis Pseudostratified Epithelium - Appears to be stratified but is actually just a single layer of cells - Nuclei appears at different levels - All cells rest on a BM, but not all reach the free surface - Helps with secretion, absorption, lubrication, transportation - Locations : ● Ciliated: lining trachea, bronchi, auditory tube, tympanic cavity, nasal cavity ● Non-ciliated: excretory passage of the male reproductive track, epididymis Stratified Epithelium Stratified Squamous - 2 or more layers of cells above the BM - Usually cuboidal shaped cells rest on the BM (polymorphic in between and squamous on top) - Non-keratinized: ● Surface cells contain nuclei ● Used for protection ● Usually “wet” ● Locations : mouth, oral pharynx, esophagus, vocal cords, and vagina - Keratinized: ● Superficial layer is composed of dead cells, cytoplasm has been replaced with keratin ● Impermeable to water ● Used for protection ● Locations: epidermis of the skin Stratified Cuboidal - Contains 2 layers of cuboidal cells - Locations : duct of sweat glands and other highly specialized areas (seminiferous epithelium of testis)

Stratified Columnar - Usually overlies a layer of cuboidal - Uncommon - Locations: conjunctiva of the eye, large excretory ducts (bile ducts), male urethra Transitional Epithelium - The transition between stratified columnar and stratified squamous - Location : exclusively in the urinary system (lines the renal calyces to the urethra) - Helps to stretch - KEY ID: dome-shaped/binucleated cells Glands - Originate from epithelial cells, leave the surface into the underlying connective tissue and produce their own BM Exocrine Glands - Leads to a duct system - Unicellular glands ● Primary example → goblet cells(lines the digestive and respiratory tract) ● Secretes mucous via exocytosis - Multicellular glands 1. Simple glands → no branching ● Simple tubular (branched) glands locations: gastric glands with 3 types of secretory proteins (epithelial mucous cells, parietal cells (HCL), chief cells (pepsin)) ● Simple tubular gland location: large intestine 2. Compound glands → ducts do branch ● Acinar (branched) gland location: exocrine pancreatic gland ● Compound tubuloacinar (branched) gland location: salivary gland

Endocrine Glands - Ductless glands composed of clumps or chords of secretory cells which secrete hormones directly into the bloodstream Lecture 2: Connective Tissue Cellular component: - Fixed cells: mesenchyme cells, fibroblasts, myofibroblasts, adipose cells, macrophages, mast cells - Transient cells: plasma cells, lymphocytes, neutrophils, macrophages - Active fibroblasts KEY ID: Dark stained, large, granular, oval-shaped nucleus with a well-defined nucleolus - Inactive fibroblasts KEY ID : Smaller, oval-shaped cell body, nucleus is smaller and elongated Adipose Cells - Fat cells or adipocytes - Two major cell types: ● Single, large lipid droplet → unilocular fat cell → forming white adipose tissue ● Multiple, small lipid droplets → multilocular fat cells → brown adipose tissue White Adipose Cells - Large spherical cells, shape changes when crowded, polyhedral shape - Store fat in the form of a single droplet - KEY ID: Usually displaces the cytoplasm and nucleus to the periphery, near the cell membrane - Septa may divide groups of adipose cells into lobes, septa is CT Brown Adipose Cells - Smaller and more polygonal than WAC - Store fat in many droplets - Spherical nucleus, not pushed to the periphery of the cell

- Many mitochondria Macrophages - KEY ID: Nucleus is irregular (usually dented on one side, kidney-bean shape) ● Cell surface is uneven ● Varying from short projections to long finger-like projections - Nucleus is smaller and stains darker than fibroblasts - Little cytoplasm can be seen ● Cytoplasm is basophilic and contains many small vacuoles and dense granules - Important in body defence and immune response/function Mast Cells - Largest of fixed cells - Ovid shape, centrally located nucleus - Large with a lightly basophilic cytoplasm and a small, pale-staining, centrally placed, spherical nucleus - KEY ID : Numerous granules in the cytoplasm (very large) - Play a role in immune response and inflammation Plasma Cells - KEY ID: “clockface”, round, eccentrically located nucleus due to the clumps of chromatin - Basophilic cytoplasm - Important in antibody production Loose Connective Tissue - Found filling in the spaces of the body Composition - Ground substance ● Soft → GAGs, e.g., hyaluronic acid, found in synovial fluid, vitreous humour ● Firm → made of GAGs, e.g., chondroitin sulphate, found in bone GS - Proteoglycans: aggrecan found in cartilage and connective tissue proper - Glycoproteins: laminin found in the BM

Fibrous Component Collagen Fibres - Most abundant - Gives CT great tensile strength and provides the architectural framework, no elasticity - 3 alpha helices come together to form a tropocollagen molecule - Type I: connective tissue proper, bone, dentin, tendons, ligaments, skin - Type II: cartilage - Type III (reticular fibres): blood vessels, lung, spleen, liver, lymph nodes, smooth muscle - Type IV: BM - Type V: associated with Type I - Type VII: secures BM to underlying CT Elastic Fibres - Made of an elastin core surrounded by a sheath of microfibrils - Composed of elastin, contains the unusual aa desmosine and isodesmosine - Do not occur in bundles but as isolated branching threads in loose CT or in prominent layers surrounding large arteries - Gives CT its elastic properties - Found in blood vessels, skin, cartilage, lungs, urinary bladder Reticular Fibres - Type III collagen - Usually in the form of a network - Forms the structural framework of the spleen, liver, lymph node, and smooth muscle Dense Connective Tisse - Have many more fibres and fewer cells - Orientation and arrangement of collagen fibres make it resistant to stress - Two subclasses: Dense irregular and Dense regular Dense Irregular CT - Random arrangement of collagen fibres → fibres are packed tight, little room for GS - Fibroblasts key cell feature → located between the collagen fibres

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