chapter 4: tissues

what are the 4 tissues of the body

  • epithelial tissue (covering)

    • covers exposed surfaces

    • lines internal passageways

    • forms glands

  • connective tissue (support)

    • fills internal spaces

    • supports other tissues

    • transports materials

    • stores energy

  • muscle tissue (movement)

    • specialized for contraction

    • skeletal muscle, heart muscle and walls of hollow organs

  • neural tissue (control)

    • carries electrical signals from one part of the body to another

key concepts

  • tissues are collections of cells and cell products that form specific, limited functions

  • 4 tissues - epithelial, muscular, connective and neural

epithelial tissues

  • epithelia: layers of cells covering internal or external strands, thin

  • glands: structures that produce secretions

characteristics of epithelia

  • cellularity (cell junctions)

  • polarity (apical and basal surfaces)

  • attachment (basal lamina)

  • avascularity

  • regeneration

functions of epithelial tissue

  • provide physical protection

  • control permeability

  • provide sensation

  • produce specialized secretions (glandular epithelium)

microvilli: increased absorption or secretion

cilia: moves fluids

free surface and attached surface

  • polarity

    • apical and basolateral surfaces

effective barriers

  • integrity maintained by

    • intercellular connections

    • attachment to basal lamina

    • maintenance and repair

intercellular connections

  • support and communication

large connections

  • cams (cell adhesion molecules)

    • transmembrane proteins

  • intercellular cement

    • proteoglycans

  • hyaluronan (hyaluronic acid)

    • glycosaminoglycans

cell junctions

  • tight junctions (sealed)

  • gap junctions

  • desmosomes (buttons) + hemidesmosomes (1/2)

basal lamina

  • lamina lucida

    • thin layer

    • secreted by epithelia

    • barrier to proteins

  • lamina densa

    • thick fibers

    • produced by connective tissue

    • strength and filtration

repairing and replacing

  • epithelia are replaced by division of germinative cells (stem cells)

  • near basal lamina

classes of epithelia

squamous epithelia

  • simple squamous epithelium

    • absorption and diffusion

  • mesothelium

    • lines body cavities

  • endothelium

    • lines heart and blood vessels

stratified squamous epithelium

  • protects against attacks

  • keratin proteins add strength and water resistance

cuboidal epithelia

  • simple cuboidal epithelium

    • secretion and absorption

  • stratified cuboidal epithelium

    • sweat and mammary ducts

stratified cuboidal epithelia

  • sweat gland ducts

transitional epithelium

  • urinary bladder

glandular epithelia

  • endocrine glands

    • release hormones, no ducts

  • exocrine glands

    • secretions through ducts

columnar epithelia

  • simple columnar epithelium

    • absorption and secretion, intestinal lining

  • pseudostratified columnar epithelium

    • cilia movement, trachea

  • stratified columnar epithelium

    • protection, salivary gland ducts

modes of secretion

  • merocrine secretion

    • sweat glands, released by vesicles (exocytosis)

  • apocrine secretion

    • mammary glands, released by shedding cytoplasm

  • holocrine secretion

    • sebaceous (oil) glands, released by cells bursting, gland cells replaced by stem cells

goblet cells: the only unicellular exocrine glands, intestinal lining

connective tissue

functions

  • forms capsule surrounding organs (serous membrane)

  • tendons and ligaments

  • skeletal system

  • fat storage

  • cushioning and insulating

  • transporting

  • protection

cells of connective tissue

  • building → -blast → fibroblasts, chondroblasts, osteoblasts

  • breaking → -clast → osteoclasts

  • cell → -cyte

loose connective tissue

  • loose (areolar): protein fibers that form a lacey network with fluid filled spaces

  • contains: collagen, reticular and elastic fibers

  • cells: fibroblasts, microphages and mast cells

  • located: throughout body

  • function: packing and nourishment

dense connective tissue

  • thick bundles of collagen fibrils densely packed with little to no extracellular matrix

  • fibers are oriented in the same direction

    • located: tendons and ligaments

    • function: withstands forces with great strength

adipose tissue

  • cells are full of lipids, little extracellar matrix

  • location: subcutaneous areas, mesenteries, renal pelvis

  • function: packing material, thermal insulation, energy storage, protection

blood

  • vascular tissue

  • blood cells surrounded by non living fluid matrix (plasma)

  • fibers - only visible during clotting

  • atypical connective tissue

8 cell types of connective tissue proper

  • macrophages

    • large amoeba like cells in immune system

    • eat pathogens and damaged cells

    • fixed stay in tissue

    • free migrate

  • adipose

    • fat

  • mesenchymal cells

    • stem cells that respond to injury or infection

    • differentiate into fibroblasts, macrophages and more

  • melanocytes

    • coloration

  • mast cells

    • stimulate inflammation after injury or infection

    • basophils are mast cells carried by blood

  • lymphocytes

    • specialized immune cells in lymphatic system

  • microphages

    • phagocytic blood cells

    • respond to signals from macrophages and mast cells

loose connective tissues

  • areolar

    • least specialized

    • open framework

    • elastic fibers

    • holds blood vessels and capillary beds

  • adipose

    • white fat

      • most common

      • stores fat

      • insulator

    • brown fat

      • more vascularized

      • breaks down fat

      • produces heat

    • adipocytes do not divide but mesenchymal cells divide and differentiate

  • reticular

    • support

muscle tissue

  • contracts and shortens, responsible for movement

    • ex striated skeletal, striated cardiac, non-striated smooth

nervous tissue

neural tissue

  • can see neurons

  • ability to conduct electrical impulses

2 types of cells

  • neurons - communication among neurons in brain

    • conscious and unconscious though processes

    • info relayed by frequency and pattern of impulses

  • neuroglia or glia cells

    • support/repair/supply nutrients

neuron

tissue repair

tissue injuries and repair

  • tissues respond to injuries to maintain homeostasis

  • cells restore homeostasis with 2 processes

    • inflammation

      • caused by body releasing histamine

      • tissue’s first response to injury

    • regeneration

heparin is a blood thinner