Tissues and Membranes Flashcards
Tissues
Collections of specialised cells, and cells products, that perform a relatively limited number of functions
Histology
The study of tissues
Epithelial
Covers exposed surfaces, lines internal passageways and forms glands
Connective
Fills internal spaces, provides structural support for other tissues, transports materials and stores energy
Muscle
Contracts for active movement
Neural
Carries information via electrical impulses
Epithelial Tissue: Characteristics
- Made of cells
- Apical and basal layers
- Attachment: Basal lamina
- Avascular
- Can regenerate
- Polarity: differences between exposed (apical) and attached (basal) surface
Epithelial Tissue (Functions)
Provide physical protection: protect exposed and internal surfaces from physical, chemical and biological elements
Control permeability: any substance entering or leaving the body must cross epithelium; level of permeability dependent on function and location within the body
Provide sensation: large sensory nerve supply which provide information about internal and external environments
Produced specialised secretions: Gland cells: discharge secretions onto the surface of epithelium or into surrounding interstitial fluid
Classification of epithelial Tissue
- Cell layers: simple (one layer), stratified (2 or more layers), pseudostratified (appear to have many layers but all cells are attached to basement membrane)
- Cell shape: squamous (flat and thin), cuboidal (cubes), columnar (tall and thin), transitional (change shape from flat to cuboidal)
Simple squamous
- Reduces friction, performs absorption and secretion
- Location: blood vessels, portions of kidney tubules (nephron loops)
Simple Cuboidal
- Limited protection, secretion, absorption
- Location: glands, ducts, thyroid gland
Simple columnar
- Protection, secretion, absorption
- Location: lining of stomach, intestine, gallbladder
Pseudostratified Columnar Epithelium
- Protection, secretion
- Location: lining of nasal cavity, trachea, bronchi
Stratified Squamous
- Protection
- Location: skin, mouth
Stratified cuboidal (relatively rare)
- Protection
- Location: Glands
Stratified columnar (relatively rare)
- Protection, secretion
- Location: Urethra
Transitional
- Permits expansion and recoil after stretching
- Location: urinary bladder, renal pelvis
Intercellular Connections: Tight junction
- Formed by the fusion of the outer layers of two plasma membranes
- Prevent diffusion of fluids and solutes between cells
- Adhesion belt lies deep to tight junction: tied to microfilaments of the terminal web
Intercellular Connections: Gap junction
Permit the free diffusion of ions and small molecules between two cells
Intercellular Connections: Desmosome
CAMs and proteoglycans link opposing plasma membranes. Resist stretching and twisting
Intercellular Connections: Desmosome: Spot Desmosomes
- Small discs connected to bands of intermediate filaments
- Function to stabilise shape of cell
Intercellular Connections: Desmosome: Hemidesmosomes
- Rather than attaching one cell to another, attaches a cell to extracellular filaments in the basement membrane
Attachment to Basement Membrane
The inner surface of each epithelium is connected to a two-part basement membrane consisting of a clear layer and a dense layer
Epithelium Maintenance and Repair
Divisions by germinative cells continually replace the short-lived epithelial cells
Glands: Specialised epithelia: Endocrine
Release hormones into surrounding interstitial fluid which then diffuse into the bloodstream. These hormones regulate metabolic and physiological process to maintain homeostasis.
Glands: Specialised epithelia: Exocrine
Release exocrine secretions into ducts which then empty onto the surface of covering and lining epithelium. Secretions include mucus, sweat, oil, earwax, saliva
Types of Secretions
- Serous glands: secretes watery solution containing enzymes
- Mucous glands: secretes mucin (creating mucus)
- Mixed exocrine glands: combination of serous and mucous glands
Modes of Secretion
- Merocrine secretion: released from apical surface by exocytosis e.g. salivary gland
- Apocrine secretion: apical portion of cell breaks off and cell repairs e.g. mammary gland
- Holocrine secretion: cell ruptures; cell replaced e.g. sebaceous gland
Connective tissue (characteristics)
- Connect epithelium to the rest of the body (basal lamina)
- Provide structure (bone)
- Store energy (fat)
- Transport materials (blood)
- No contact with environment
Connective Tissue (functions)
- Connection: binds together, supports and surrounds other tissues
- Framework: establishes a structural framework for the body
- Protection: Protects and insulates internal organs
- Transportation: transports fluids and dissolved materials
- Storage: primary location of stored energy reserves
- Immune response: defends from invading microorganisms
Classification of CT: Connective Tissue Proper: Loose CT
- Areolar Tissue: Loose open framework of collagen, elastic and reticular fibres, can distort, nerves, blood vessels
- Adipose Tissue: Composed of adipocytes, provides padding and insulation, energy reserve, kidneys, beneath skin
- Reticular Tissue: Reticular fibres form 3D framework, provides support, liver, kidney, spleen
Classification of CT: Connective Tissue Proper: Dense CT
- Dense regular CT: collagen fibres arranged in parallel bundles, withstands pulling along the axis of fibres. e.g. tendons and ligaments
- Dense irregular CT: Interwoven, randomly arranged collagen fibres, strengthens and supports in multiple directions. e.g. fascia, around muscles and organs
- Elastic Tissue: Predominantly elastic fibres, allows tissue to tolerate cycles of expansion and recoil. e.g. spinal column between vertebrae
Classification of CT: Connective Tissue Proper: Fluid CT (transportation and immune response)
- Blood: Plasma-with suspended proteins, blood cells, fragments of cells
- Lymph: Watery matrix - fewer proteins than blood, leukocytes, maintain homeostasis
Classification of CT: Connective Tissue Proper: Supportive CT (framework) - cartilage
- Hyaline Cartilage: collagen fibres, not in large bundles, stiff but flexible support. e.g. between ribs, bronchi
- Elastic cartilage: contains numerous elastic fibres, tolerates distortion without damage, returns to original shape. e.g. ear
- Fibrocartilage: densely woven collagen fibres, little ground substance, combination of strength and rigidity, strongest cartilage. e.g. knee joint
Classification of CT: Connective Tissue Proper: Supportive CT (framework) - bone
- small volume of ground substance
- Matrix dominated by calcium salts, with the remainder mainly collagen fibres
- strong, flexible and resistant to shattering
- blood vessels branch through matrix
Neural tissue
Neuron: transmit electrical impulses
Neuroglia: support, repair tissue
Cell body
‘life support’
Axon
carries messages
dendrites
collect signals from other cells to go back to soma
Muscle tissue
- Skeletal (face expression attached to bones): multinucleated, striated, voluntary
- Cardiac (heart): mononucleated, striated, involuntary
- Smooth (blood vessels): mononucleated, non-striated, voluntary
Membranes: Mucous
- Lines body cavities that open directly to the exterior
- Kept moist to reduce friction, either by mucous or other fluids
- e.g. Lungs
Membranes: Serous
- Lines internal body cavities
- Serous fluid allows organs to glide over each other easily
Membranes: Cutaneous
- Covers body surfaces
- Thick and dry, protects underlying tissue
- e.g. skin
Membranes: Synovial
- Lines joint cavities
- Synovial fluid, lubricates cartilage
- Does not have true epithelium
Layers of Connective Tissue: Superficial Fascia
- Between skin and underlying organs
- Areolar tissue and adipose tissue
- Also known as subcutaneous layer of hypodermis
Layers of Connective Tissue: Deep Fascia
- Bound to capsules, tendons, ligaments
- Dense CT
- forms a strong, fibrous internal framework
Layers of Connective Tissue: Subserous Fascia
- Between serous membranes and deep fascia
- Areolar tissue
CT proper cell population: fibroblasts
- secrete hyaluronan and proteins that interact to form proteoglycans that make the ground substances viscous: also secretes protein subunits that form extracellular fibres
CT proper cell population: Fibrocytes
Maintain connective tissue proper fibres
CT proper cell population: Adipocytes
Fat cells, store energy
CT proper cell population: Mesenchymal cells
Stem cells, divide to form stem cells that differentiate
CT proper cell population: Macrophages
Phagocytic cells; engulf damaged cells or pathogens
CT proper cell population: Mast cells
Release histamine and heparin in inflammation
CT proper cell population: Lymphocytes
White blood cell, part of immune response
CT proper cell population: Microphages
Phagocytic blood cells; assist macrophages and mast cells in injury or infection
CT proper cell population: Melanocytes
Stores pigment (melanin)
