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Flashcards in Tissues Deck (71):
1

Types of primary tissue

Muscle, nervous, epithelial, connective

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Squamous epithelial cell

Width > height, irregular shape, central nucleus

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Cuboidal epithelial cell

width = height, isodiametric, central nucleus

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Columnar epithelial cell

Height > width, basal nucleus

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Simple epithelial cell

1 cell layer thick, all contact BM, selective diffusion, absorption, secretion

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Stratified epithelial cell

Multiple cell layers, only base contacts BM, protective surfaces, named by apical surface cells, but more than one shape

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Pseudostatified epithelial cell

Only 1 cell , appears multilayer, all BM contact, not all contact lumen, larger airways or respiratory tract

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Presence of surface extensions on epithelial cells

Ciliated, microvilli

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Properties of surface layer

Keratinised (no nuclei), non-keratinised

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Exchange epithelia

Simple squamous, very thin, flattened, allow gas exchange e.g. endothelial cells

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Transporting epithelia

Selective exchange of non gases, digestives, kidney, columnar/cuboidal, thick simple, microvilli on apical, tight junctions, numerous mitochondria

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Ciliated epithelia

Non-transporting, move fluid and particles, respiratory system

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Protective epithelia

Stratified, all shapes, epidermis, oesophagus

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Secretory epithelia

Produce substances --> EC space, isolated/groups i.e. gland. Exocrine cells contain a duct - serous secretions or mucous secretions. Endocrine is ductless and secretes hormones - pancreas and thyroid

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Cilia

Extension of cytoskeleton, core of microtubules, can move and can move substances over surface e.g. respiratory tract. Microtubules within ciliary membrane - transition fibres basal body

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Microvilli

v small (700nm), Highly absorptive cells in SI and kidney tubules - increase in SA. Shape maintained by actin filaments. Do not move.

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Basolateral folds

Deep invaginations of lateral surface of cell, ion transport, inc SA, mitochondria, renal tubule cells

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Intercellular junctions

Selective maintain seal between EC

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Tight junctions

Attaches cells to each other via cytoskeleton - structural strength

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Adherens junctions and desomsomes

allow cell to cell communications via substances - gap junctions

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Connexins

Pore opening regulation

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Anchoring junctions

structural strength by linking epithelium to underlying BM

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Functions of basal lamina

Structural attachment
Compartmentalisation - isolates epithelia, muscle and nerves from connective tissue
Filtration - selective movement to and from CT
Tissue scaffold - repair after damage and guides to new locations
Signalling - regulation of EC behaviour

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Glandular epithelia

Secretory cells organised into groups --> large organ

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Exocrine

Product secreted by a duct, simple glands = simple cuts, compound glands = branched gut

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Endocrine

Ductless, secreted directly into bloodstream - hormones

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Exocrine secretory mechanisms

Merocrine - membrane bound vesicles containing product fuse with plasma membrane (exocytosis)
Apocrine - release of product in membrane bound vesicles, surrounded by cytoplasm and plasma membrane
Holocrine - whole cell containing product undergoes programmed death and is shed

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Endocrine secretory mechanism

Exocytosis of product from cell diffuses into bloodstream

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Secretory products

Proteins, mucus, steroids

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Connective tissue functions

Connects, supports, anchors, physical barrier - blood, cartilage and bone

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Types of connective tissue

Loose CT - no fibres, many cells
Dense, irregular CT - muscle, nerve sheets
Dense, regular CT - packed with collages, tendons, ligaments
Mobile (defence) and fixed (maintenance, repair, energy store)

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Fibronectin

Multifunctional glycoprotein - mediates adhesion between a wide range of cells and ECM components

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Fibroblasts

Make collagen (stretch)

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Classification of CT

CT proper - loose, dense
Specialised CT - bone, cartilage, adipose tissue, blood, haematopoetic, lymphatic

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Dense irregular CT

Collagen fibres, little ECM, strength, collagen irregular bundles, specific types - intestinal submucosa, reticular or deep later of dermis

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Dense regular CT

Main constituent of ligaments, tendons and aponeuroses

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Tendons

Parallel bundles collagen fibres with fibroblast rows in between collagen I - lack elastic fibres, tendinocytes secrete ECM mechanically isolating from load bearing collagen fibrils, tendon as a whole surrounded by CT capsule, often extends to tendon --> subsections, outer capsule collagen fibres less regularly orientated - epilendinium, CT petitioning tendon contains nerves and blow vessels - endotendinium.

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Ligaments

Ligaments and fibroblasts in parallel - less regularly orientated than in tendons, mostly collagen, nervous = elastic fibres

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Aponeuroses

Collagen fibres in layer - 90 degrees yo each other

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Collagen fibres and fibrils

Most abundant fibre type, flexible, high tensile strength, over 20 types, diameter varies, 300nm dense regular CT/ tendons, individual fibres straight, overlapping network

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Reticular fibrils

Collagen III (younger), 20nm wide, branched, boundary CT/epithelium, around adipocytes (fat cells), small blood vessels, nerves and mulches, supporting stroma of haematopoeitci and lymphoid tissues, not thymus. Tissue immaturity - embryonic, initial stages wound healing and scar formation. Quick strength, replace eventually stronger the I collagen.

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Where is collagen produced?

Fibroblasts, Schwann cells in endoneurium of peripheral nerves and smooth muscle cells

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Elastin fibres

Thinner than collagen and coiled, covalent links to other elastin - 3D mesh interwoven with collage to prevent tearing.

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Where are elastin fibres produced?

Fibroblasts, SM, central core surrounded by fibrillar

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Extracellular matrix

Different proportions of ECM components secreted by tissues - properties, mechanical and structural support. Tensile strength, biochemical barrier, regulates activity of cellular component - anchors, cellular migration pathways

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Proteoglycans

Glycosaminoglycans - unbranched large polysaccharides, negative charge, attract water. Covalent link to core protein.

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Multi-adhesive glycoproteins

Bind to cell surface proteins and ECM components, bind multiple surfaces

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Cellular components of CT

Fibroblasts
Myofibroblacts - secrete fibres, ECM and ma have contractile functions
Chondrocytes secrete cartilage ECM
Osteoblasts secrete bone ECM
Adipocytes - lipid storing cells
Resident cells of immune system (macrophages, mast cells and lymphocytes)

49

Functions of the skin

Protection - UV, chess, microbes
Sensation - temp, pressure, touch
Thermoregulation
Metabolic

50

Epidermis

In contact with external, down-growths - epidermal appendages - hairs, keratinocytes, melanocytes, langerhans cells, merkel cells, separated from dermis by DM

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Cell layers of epidermis

Cornified layer - dead, seal, nothing through
Granular layer
Spinous layer
Basal layer - cell free

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Keratinocytes

Main cell type in epidermis - stratified squamous epithelium. Contain keratin intermediate filaments.

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Basal keratinocytes

Production of keratinocytes, cuboidal/low columnar, mitosis - stem cells bound to BM by hemidesmososmes, bound to each other by desmosomes

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Keratinocytes in spinous layer

No mitosis, tightly bound, dark staining, change in gene expression pattern

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Keratinocytes in granular layer

Flat, no nucleus or other organelles,cells secrete lipids and change cell membrane composition, produce surface keratins

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Keratinocytes in cornified layer

Tightly packed, flattened, dead reaimsin of cells. Cornified envelope - cross-linked protein layer under membrane of cornfield cells.

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Melanocytes

Produce melanin, basal layer bound to BM, derived from neuroectoderm, relatively constant numbers, activity genetically variable, pale staining.
Melanoprotein complexes pass through processes --> keratinocytes - on top of nuclei to protect.

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Langerhans cells

Recognise antigen and present to T cells - all layers, mainly spinous, cytoplasmic processes extending between cells, pale staining

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Merkel cells

Specialised epithelia - sensory receptors to light touch - basal layer. Synaptic junctions with peripheral nerve endings

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Dermis

Layer of supporting tissue on which epidermis sits, nerves, blood vessels, fibroblasts, fibrocytes, macrophages, lymphocytes, mast cells, ECM - collagen, elastic fibres. Thin and vertical

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Layers of dermis

Papillary dermis - less collagen and elastic fibres, more glycogen, small caps. Thin and vertical.
Reticular dermis - dense collagen and thick elastic fibres, major blood vessels and lymphatics - darker stain. Thick and horizontal .

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Hypodermis or subcutis

Deepest skin layer - adipose and collagen fibres, come epidermal appendages, major blood supply and nerves, insulator, shock absorber and food store

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Hair follicles

Tubular structure - hair follicle, shaft, arrestor pili musacee and sebaceous gland. Differ in places - head = 2 year turn over, body hair = short growing phase.

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Sebaceous gland

Outgrowth from external root sheath, branched acinar gland, produces sebum - lipids and complex waxes - coats hair and skin, holocrine secretion - cells die and release contents into duct, arrestor pili muscle aids expelling secretion

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Eccrine or merocrine sweat glands

All over body - large chilled tubular gland with duct - surface secretes clear hypotonic water liquid, slightly acidic, rich sodium, potassium, urea and cl. Regulates body temp, controlled autonmic

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Apocrine sweat glands

Genetalia, anus, armpits, hair follicle rich areas. Large coiled tubular gland with large lumen and duct --> surface or into hair follicle. Milky viscous oily liquid, microbial activity --> strong odour, mark territory, sexual attraction

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Free nerve endings

In epidermis - pain, itch, temp, non/myelinated

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Merkels discs

Epidermis - touch

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Pacinian corpuscle

Lower dermis - pressure, vibration, encapsulated nerve endings

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Meissners corpuscle

upper dermis - touch, encapsulated nerve endings, spirally arranges, hands and feet

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Organ of Ruffni

Dermis - mechanoreceptor - encapsulated nerve endings, thin walled fluid filled capsule, fine nerve branches, collagen fibres pass through