HLSC-1200U Week 3 Definitions

Histology

microscopic study of tissue appearance

Tissue Membranes

thin layer of cells that covers external body surfaces. organs, internal passages and cavities

Epithelial Membranes

• Epithelium attached to a layer of connective tissue

Mucous Membrane (Mucosa)

• lines internal cavities that open externally

• produces mucus and has underlaying connective tissue

Ex: digestive tracts

Serous Membrane (Serosa)

• lines cavities and organs that do not open externally

• produces serious fluids

Ex. Pleura

Cutaneous Membrane (Skin)

• covers external body surface

• Keratinized cells protect the body from desiccation and pathogens

Properties of Epithelial Tissue

• Cells connected by cell junction w/ little extracellular material

• Avascular; thickness limits nutrient + waste exchange

• Capable of reproduction; necessary because of wear and tear

Functions of Epithelial Tissue

• Protection from injury and foreign pathogens

• Sensory functions

• Produces secretions

• Barrier to control movement of gases, solutes and fluid

Structure of the Epithelial Tissue

Organized into layers

• Apical (free) Surface: interacts with external environment

• Basement Membrane: permeable material linked to connective tissue

Types of Epithelial Tissue

• Membranous Epithelium: lines serious cavities, blood/lymphatic vessels

• Glandular Epithelium: secretory units of endocrine and exocrine glands

Anchoring Junctions

• Common on lateral and basal surfaces of cells

• Strong, flexible connections

Desmosomes

cadherin (adhesion protein) link adjacent cell membranes

Hemidesmosomes

integrin (adhesion protein) link cells to basal lamina

Adherens Junctions

Actin (contractile protein) link patches

Tight Junctions

No extracellular space between cells

• Stops substances moving between cells

• Separates cells into apical and basal compartments

Gap Junctions

forms intercellular passageways between membranes

• Allows substances to move quickly between cytoplasm of adjacent cells

• Allows coordination of function in a large group

Simple Squamous Epithelium

absorption + secretion
Ex. lining of alveoli

Simple Cuboidal pithelium

absorption + secretion

Ex. lining of glands

Simple Columnar Epithelium

absorption + secretion

Ex. lining of bronchi

Stratified Squamous Epithelium

protection

Ex. lining of skin

Stratified Cuboidal Epithelium

protection

Ex. lining of sweat gland

Stratified Columnar Epithelium

protection

Ex. lining of male uretha

Pseudostratified Columnar Epithelium

secretion

Ex. lining of trachea

Transitional Epithelium

allows urinary organs to expand and stretch

Ex. lining of bladder

Glands

modified epithelium cells that can synthesize and secrete chemical substances

Exocrine Glands

• secretes mucous, sweat, saliva, breast milk

• secretions leave through a duct that opens to the external environment

Ex. sweat glands

Endocrine Glands

• ductless gland that releases secretions directly into surrounding tissues and fluids

Ex. thymus

Merocrine Secretions

• most common

• Enclosed in vesicles + released by exocytosis

• Causes little damage to the cell

Ex. watery mucous

Apocrine Secretions

• Pinched off from the cell membrane and released to cause little damage to the cell

Ex. apocrine sweat glands in genital areas

Holocrine Secretions

• Released when cells burst

• Destroys entire gland cell

Ex. Sebaceous glands that produce oils

Connective Tissue

supports + connects other tissues

Fibroblast

• Most common cell type

• Secretes polysaccharides and proteins

Fibrocyte

• More mature form of fibroblast

Adipocyte

• Stores lipids in cytoplasm

Mesenchymal Cell

• multipotent adult cell involved in repair and healing

Macrophage

• phagocytes which also secretes cytokines to recruit other immune cells

Mast Cells

involved in inflammatory response

Collagen FIbers

• Fibrous proteins linked to form a straight fiber

• Flexible, resists stretching

Ex. Ligaments and tendons

Elastic Fibers

• contains elastin protein and some glycoproteins

• returns to its original shape after being stretched

• Ex. elastic tissues in skin

Recticular Fibers

• In a branching network

• flexible, great strength, resists stretching

Ex. reticular tissue of liver

Extracellular Matrix

• Attracts + traps moisture to form a clear, colourless matrix

• Formed by proteins and polysaccharides

Dense Connective Tissue

• contains more collagen fibers to loose connective tissue to provide greater resistance to stretch/resists stretching in other directions

Dense Regular Connective Tissue

• fibers arranged parallel to each other

• Greater strength in one direction

Ex. Ligaments

Dense Irregular Connective Tissue

• fibers arranged in random directions

• Greater strength in all directions

• can regain original shape after stretching

Ex. walls of arteries

Loose Connective Tissue

• absorbs shock

• binds tissues

• allows diffusion

Adipose Tissue

• consists of fat storage w/ little extracellular matrix

• large number of capillaries

• rapid storage

• mobilization of lipid molecules

Areolar Tissue

• distrubuted to fill spaces between muscle fibers

• surrounds blood vessels

• supports organs

Reticular Tissue

• framework for soft organs

Ex. spleen

Cartilage Tissue

• Avascular

• Slow diffusion of nutrients through the matrix

Chondroblasts

• most active developing cartilage cells

Chondrocytes

• Less active

• more mature cartilage cells

Lacunae

• Space occupied by chondrocytes

Perichondrium

• layer of dense, irregular connective tissue that encapsulates the cartilage

Hyaline Cartilage

• most common

• contains short + dispersed collagen fibers

• large amounts of proteoglycans

Ex. rib cage, nose

Elastic Cartilage

• elastic fibers + collagen and proteoglycans

• gives rigid support

Fibrocartilage

• thick bundles of collagen fibers dispersed through its matrix

Ex. intervertebral discs

Bone Tissues

• highly vascularized

• bone cells are located within lacunae

• mixture of organic compounds embedded in inorganic compounds

Fluid Connective Tissue

• cells circulate in a liquid matrix w/ no fibers

Blood

transports fluid, cells and substances throughout the body

Lymph

• consists of WBC + larger molecules that cannot enter the bloodstream directly

• collects excess fluid

• transports WBC + substances towards the thoracic and subclavian veins

Skeletal Muscle Tissue

• striated

• Inviluntary control

• produces head / protects organs

• attached to bones around entrance points to body

Cardiac Muscle Tissue

• Striated

• Involuntary control

• Pumps blood throughout the body (heart)

Smooth Muscle Tissue

• No striation

• Involuntary control

• Controls digestion, respiration, secretions

• Walls of major organs and passageways

Neuron

• releases action potentials which releases neurotransmitters to communicate with other neurons

Neuroglia

supports neurons and modulating their information

Epidermis

• stratified, squamous epithelium

• No blood vessels

• Renewed every 4-8 weeks

Thick Skin

• 5 layers

• Appears to have ridges

• Sensation, manipulation of objects

Ex. palms of hands

Thin Skin

• 4 layers

• Smooth w/ irregular grooves

• Normal skin function

• Found in most locations throughout the body

Basal Cells

• Cuboidal stem cell in the stratum basale that produces keratinocytes

Keratinocytes

• manufactures/stores keratin and water-repelling glycolipid that helps precent water loss from the body

Merkel Cells

• for sensory nerves (hands + feet)

• touch receptors

Melanocytes

• produces melanin pigment in the stratum basale

Langerhans

• Macrophages in the stratum spinosum which destroys bacteria/damaged cells

Stratum Basale

• single layer of stem cells

• always produces new cells

  • pushes to the surface

• attaches epidermis to dermis

Stratum Spinosum

• rich in RNA

• Produces keratin

Stratum Granulosum

• grainy appearance due to accumulation of lamellar granules containing keratin

• disintegrates as cell dies, releasing keratin

Stratum Lucidum

• smooth, translucent layer

• only found in thick skin

Stratum Corneum

• superficial layer

• exposed to external environment

• dry, dead cells with keratin

Melanocytes

cells that produce melanin

Melanin

• pigments that contribute to colour for hair/skin

• protects epidermis from DNA damage by UV radiation

Melanosomes

vesicles of melanin produced by melanocytes

Melanosomes are ingested by surrounding keratinocytes and form a cap over the nucleus, this protecting it from DNA damage

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Dermis

• deep in the epidermis

Papillary Layer

• loose, areolar connective tissue

• provides elasticity, connection strength with epidermis

Reticular Layer

• Deep, thick layer of dense, irregular tissue

• provides elasticity, structure and strength

• collagen binds to water to keep the skin hydrated

Hypodermis

• below the dermis to connect skin to bones and muscles

• loose, well vascularized

• fat storage, insulates/cushions the integumentary system