HISTOLOGY The Study of Body Tissues: Epithelial, Connective, Muscle, Nervous

BODY TISSUES  Tissues … Groups of cells with similar structure and function … Four primary types  Epithelial tissue (epithelium)  Connective tissue  Muscle tissue  Nervous tissue

EPITHELIAL TISSUES: MEMBRANEOUS  Locations … Body coverings … Body linings- digestive & respiratory tract  Functions … Protection … Absorption … Filtration … Secretion

EPITHELIUM CHARACTERISTICS  Cells fit closely together and often form sheets  The apical surface is the free surface of the tissue, covers major glands  The lower surface of the epithelium rests on a basement membrane  Avascular (no blood supply)  Regenerate easily if well nourished

EPITHELIAL TISSUE: GLANDULAR  Glandular secretes from endocrine & exocrine glands

EPITHELIUM CHARACTERISTICS

CLASSIFICATION  Shape of cells … Squamous: flat, single layer … Cuboidal: cube- shaped … Columnar: column … Transitional: change form squamous to cuboidal

CLASSIFICATION  Number of cell layers … Simple—one layer … Stratified—more than one layer … Pseudostratified- appears as many layers but only one

SIMPLE EPITHELIA  Simple squamous … Single layer of flat cells … Tightly packed … Permeable to oxygen thru diffusion … Lines body cavities  Lines lungs and capillaries

SIMPLE EPITHELIA

 Simple cuboidal … Single layer of cube-like cells … Common in glands and their ducts … Secretes & absorption … Forms walls of kidney tubules … Covers the ovaries

SIMPLE EPITHELIA

 Simple columnar … Single layer of tall cells … Often includes mucus-producing goblet cells … Nuclei near bottom … Absorption, secretion & transport … Cells with microvilli for absorption … Lines digestive tract & uterus

SIMPLE EPITHELIA

 Pseudostratified columnar … Single layer, but some cells are shorter than others, varying heights … Often looks like a double layer of cells … Sometimes ciliated, such as in the respiratory tract … May function in absorption or secretion

SIMPLE EPITHELIA

STRATIFIED EPITHELIA  Stratified squamous … Many layers of flat cells … Found as a protective covering where friction is common, wear & tear … Locations  Skin, Mouth, Esophagus & Vagina

STRATIFIED EPITHELIA

 Stratified cuboidal—two layers of cuboidal cells  Stratified columnar—surface cells are columnar, cells underneath vary in size and shape  Stratified cuboidal and columnar … Rare in human body … Found mainly in ducts of large glands

STRATIFIED EPITHELIA  Transitional epithelium … Shape of cells depends upon the amount of stretching … Multiple layers, change from squamous to cube … Lines hollow organs, under stress: bladder … Lin

STRATIFIED EPITHELIA

GLANDULAR EPITHELIUM  Gland … One or more cells responsible for secreting a particular product … Cells are responsible for producing and secreting

GLANDULAR EPITHELIUM  Two major gland types … Endocrine gland  Ductless since secretions diffuse into blood vessels  All secretions are hormones … Exocrine gland  Secretions empty through ducts to the epithelial surface  Include sweat and oil glands

GLANDULAR EPITHELIUM

GLANDULAR TYPES  Apocrine: Secretion results in damage to cell membrane & loss of cytoplasmEX: mammary glands  Holocrine: Secretion products causes rupture & death of cell EX: sebaceous glands/ oil glands  Merocrine: Most numerous, secretion w/o loss of cytoplasm EX: sweat glands

CONNECTIVE TISSUE  Found everywhere in the body  Includes the most abundant and widely distributed tissues  Functions … Binds body tissues together … Supports the body … Provides protection … Transports

CONNECTIVE TISSUE CHARACTERISTICS  Variations in blood supply … Some tissue types are well vascularized … Some have a poor blood supply or are avascular  Extracellular matrix … Non-living material that surrounds living cells … Defines connective tissue characteristics … Matrix may be solid, gel or liquid w or w/o fibers

EXTRACELLULAR MATRIX Types of Fibers: Three types … Collagen: made of collagen- tough & stingy Bundles for strength, protein, white … Elastic yellow fibers, stretches- elastic & returns to original length after stretch, found in come cartilage … Reticular fibers: delicate, in networks, found in capillaries & nerve fibers

CONNECTIVE TISSUE TYPES  Loose connective tissue types … Areolar tissue  Most widely distributed connective tissue  Soft, pliable tissue like “cobwebs”  Functions as a packing tissue  Contains collagen & elastic fibers  Can soak up excess fluid (causes edema)  Found between skin & muscle- Fascia

CONNECTIVE TISSUE TYPES

 Loose connective tissue types … Adipose tissue  Matrix is large lipid deposits  Functions … Insulates the body … Protects & supports some organs … Serves as a site of fuel storage … found thruout body

CONNECTIVE TISSUE TYPES

 Loose connective tissue types … Reticular connective tissue  Delicate network of interwoven fibers  Forms network of lymphoid organs Found in Lymph nodes, Spleen, Bone marrow Function is to defend against microorg. & filter out harmful particles Phagocytocize

CONNECTIVE TISSUE TYPES

 Dense fibrous tissue Main matrix element is collagen fiber Provide strong connections & flexibility … Locations  Tendons—attach skeletal muscle to bone  Ligaments—attach bone to bone at joints  Dermis—lower layers of the skin

CONNECTIVE TISSUE TYPES

 Bone (osseous tissue) … Composed of  Bone cells: osteocytes  Hard matrix of calcium salts  Large numbers of collagen fibers … Used to protect, support, mineral reserve & muscle attachement

CONNECTIVE TISSUE TYPES

 Hyaline cartilage … Most common type of cartilage … Composed of: collagen fibers, rubbery/gel matrix- shiny & translucent … Contains chondrocytes (cartilage cells) … Avascular … Locations: End of articulating bones, fetal skeleton prior to birth

CONNECTIVE TISSUE TYPES

 Elastic cartilage … Provides elasticity & flexibility … Has fine elastic fibers to make it more bendable than hyaline … Location: Supports the external ear, nose

CONNECTIVE TISSUE TYPES

CONNECTIVE TISSUE Fibrocartilage Strong & durable, highly compressible Shock absorber Location: discs between vertebrae, pubic symphysis

CONNECTIVE TISSUE TYPES

 Blood (vascular tissue) … Blood cells surrounded by LIQUID matrix called blood plasma … Fibers are only visible during clotting … Functions as the transport vehicle for materials … protection

CONNECTIVE TISSUE TYPES

MUSCLE TISSUE  Specialized cells involved in contraction  Function is to produce movement  Three types … Skeletal muscle … Cardiac muscle … Smooth muscle

MUSCLE TISSUE TYPES  Skeletal muscle … Under voluntary control … Contracts to pull on bones or skin … Produces gross body movements or facial expressions … Characteristics of skeletal muscle cells  Striated  Multinucleate (more than one nucleus)  Long, cylindrical

MUSCLE TISSUE TYPES

 Cardiac muscle … Under involuntary control … Found only in the heart … Function is to pump blood … Characteristics of cardiac muscle cells  Striated  Branching ends  One nucleus per cell

MUSCLE TISSUE TYPES

 Smooth muscle … Under involuntary muscle … Found in walls of hollow organs such as stomach, uterus, and blood vessels … Characteristics of smooth muscle cells  No visible striations  One nucleus per cell  Spindle-shaped cells

MUSCLE TISSUE TYPES

NERVOUS TISSUE  Composed of neurons and nerve support cells called neuroglia  Function is to send impulses to other areas of the body … Irritability- changing nerve impulse … Conductivity- transmit nerve impulse … Found in : brain, nerves & spinal cord

NERVOUS TISSUE

TISSUE REPAIR (WOUND HEALING)  Three Phases … Inflammatory Phase  To remove injury causing agent and limiting tissue damage  Redness, swelling, heat and loss of function  Blood vessels dilate and fluid move into tissue. Blood clotting occurs.  This also allow WBC’s to move to injury to clean up bacteria and other debris

TISSUE REPAIR (WOUND HEALING)  Chemicals released to attract fibroblasts (connective tissue cells that make collagen fibers) … Proliferative Phase  Fibroblasts make collagen fibers that fill the space. Blood vessels also start to regenerate and fill the space  Surrounding cells begin to divide and form granulation tissue –new and lots of blood vessels so it’s pink

TISSUE REPAIR (WOUND HEALING)  Epitheliazation—epithelial cells divide and move into space with collagen fibers  WBC’s leave and swelling decreases so it turns white … Remodeling Phase (3 weeks – 6 months)  Collagen continues to be formed (how much depends on severity of wound)  Epithelial cells move into place  Scab detaches

REGENERATION OF TISSUES  Tissues that regenerate easily … Epithelial tissue (skin and mucous membranes) … Fibrous connective tissues and bone  Tissues that regenerate poorly … Skeletal muscle  Tissues that are replaced largely with scar tissue … Cardiac muscle … Nervous tissue within the brain and spinal cord