Tissues Flashcards
Types of primary tissue
Muscle, nervous, epithelial, connective
Squamous epithelial cell
Width > height, irregular shape, central nucleus
Cuboidal epithelial cell
width = height, isodiametric, central nucleus
Columnar epithelial cell
Height > width, basal nucleus
Simple epithelial cell
1 cell layer thick, all contact BM, selective diffusion, absorption, secretion
Stratified epithelial cell
Multiple cell layers, only base contacts BM, protective surfaces, named by apical surface cells, but more than one shape
Pseudostatified epithelial cell
Only 1 cell , appears multilayer, all BM contact, not all contact lumen, larger airways or respiratory tract
Presence of surface extensions on epithelial cells
Ciliated, microvilli
Properties of surface layer
Keratinised (no nuclei), non-keratinised
Exchange epithelia
Simple squamous, very thin, flattened, allow gas exchange e.g. endothelial cells
Transporting epithelia
Selective exchange of non gases, digestives, kidney, columnar/cuboidal, thick simple, microvilli on apical, tight junctions, numerous mitochondria
Ciliated epithelia
Non-transporting, move fluid and particles, respiratory system
Protective epithelia
Stratified, all shapes, epidermis, oesophagus
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
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
Microvilli
v small (700nm), Highly absorptive cells in SI and kidney tubules - increase in SA. Shape maintained by actin filaments. Do not move.
Basolateral folds
Deep invaginations of lateral surface of cell, ion transport, inc SA, mitochondria, renal tubule cells
Intercellular junctions
Selective maintain seal between EC
Tight junctions
Attaches cells to each other via cytoskeleton - structural strength
Adherens junctions and desomsomes
allow cell to cell communications via substances - gap junctions
Connexins
Pore opening regulation
Anchoring junctions
structural strength by linking epithelium to underlying BM
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
Glandular epithelia
Secretory cells organised into groups –> large organ
Exocrine
Product secreted by a duct, simple glands = simple cuts, compound glands = branched gut
Endocrine
Ductless, secreted directly into bloodstream - hormones
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
Endocrine secretory mechanism
Exocytosis of product from cell diffuses into bloodstream
Secretory products
Proteins, mucus, steroids
Connective tissue functions
Connects, supports, anchors, physical barrier - blood, cartilage and bone
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)
Fibronectin
Multifunctional glycoprotein - mediates adhesion between a wide range of cells and ECM components
Fibroblasts
Make collagen (stretch)
Classification of CT
CT proper - loose, dense
Specialised CT - bone, cartilage, adipose tissue, blood, haematopoetic, lymphatic
Dense irregular CT
Collagen fibres, little ECM, strength, collagen irregular bundles, specific types - intestinal submucosa, reticular or deep later of dermis
Dense regular CT
Main constituent of ligaments, tendons and aponeuroses
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.
Ligaments
Ligaments and fibroblasts in parallel - less regularly orientated than in tendons, mostly collagen, nervous = elastic fibres
Aponeuroses
Collagen fibres in layer - 90 degrees yo each other
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
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.
Where is collagen produced?
Fibroblasts, Schwann cells in endoneurium of peripheral nerves and smooth muscle cells
Elastin fibres
Thinner than collagen and coiled, covalent links to other elastin - 3D mesh interwoven with collage to prevent tearing.
Where are elastin fibres produced?
Fibroblasts, SM, central core surrounded by fibrillar
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
Proteoglycans
Glycosaminoglycans - unbranched large polysaccharides, negative charge, attract water. Covalent link to core protein.
Multi-adhesive glycoproteins
Bind to cell surface proteins and ECM components, bind multiple surfaces
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)
Functions of the skin
Protection - UV, chess, microbes
Sensation - temp, pressure, touch
Thermoregulation
Metabolic
Epidermis
In contact with external, down-growths - epidermal appendages - hairs, keratinocytes, melanocytes, langerhans cells, merkel cells, separated from dermis by DM
Cell layers of epidermis
Cornified layer - dead, seal, nothing through
Granular layer
Spinous layer
Basal layer - cell free
Keratinocytes
Main cell type in epidermis - stratified squamous epithelium. Contain keratin intermediate filaments.
Basal keratinocytes
Production of keratinocytes, cuboidal/low columnar, mitosis - stem cells bound to BM by hemidesmososmes, bound to each other by desmosomes
Keratinocytes in spinous layer
No mitosis, tightly bound, dark staining, change in gene expression pattern
Keratinocytes in granular layer
Flat, no nucleus or other organelles,cells secrete lipids and change cell membrane composition, produce surface keratins
Keratinocytes in cornified layer
Tightly packed, flattened, dead reaimsin of cells. Cornified envelope - cross-linked protein layer under membrane of cornfield cells.
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.
Langerhans cells
Recognise antigen and present to T cells - all layers, mainly spinous, cytoplasmic processes extending between cells, pale staining
Merkel cells
Specialised epithelia - sensory receptors to light touch - basal layer. Synaptic junctions with peripheral nerve endings
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
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 .
Hypodermis or subcutis
Deepest skin layer - adipose and collagen fibres, come epidermal appendages, major blood supply and nerves, insulator, shock absorber and food store
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.
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
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
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
Free nerve endings
In epidermis - pain, itch, temp, non/myelinated
Merkels discs
Epidermis - touch
Pacinian corpuscle
Lower dermis - pressure, vibration, encapsulated nerve endings
Meissners corpuscle
upper dermis - touch, encapsulated nerve endings, spirally arranges, hands and feet
Organ of Ruffni
Dermis - mechanoreceptor - encapsulated nerve endings, thin walled fluid filled capsule, fine nerve branches, collagen fibres pass through
