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

effective barriers

• integrity maintained by

  • intercellular connections

  • attachment to basal lamina

  • maintenance and repair

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

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