Anatomy and Physiology Notes -- KEY
Unit 5 -- Tissues
Connective Tissues
I. General characteristics:
functions:
bind structures, provide support, give protection,
serve as frameworks, fill spaces, store fat,
produce blood cells, repair tissue damage,
protect against infections
farther apart than epithelial cells
possess MATRIX (intercellular material made of fibers and some type
of ground substance (may be solid, semisolid, or liquid)
have good blood supplies
II. Major cell types:
1. fibroblasts: most common fixed cell, produce fibers star-shaped, large cells
(see page 104)
2. macrophages: type of WBC, function is phagocytosis, movable within and
around tissues
3. mast cells: usually found near blood vessels, produce and release
HISTAMINE (allergies) and HEPARIN (inflammation)
III. Connective tissue fibers:
1. collagenous fibers: thick protein (collagen) threads, grouped in
bundles. Strong, flexible, but not very elastic
function: hold structures together
found in: ligaments (bone to bone), tendons (muscle to bone)
dense connective tissue: tissue that has collagenous fibers
appears white (AKA: white fibers)
2. elastic fibers: made of elastin (protein), form branching networks
not as strong as collagenous fibers, but can easily stretch
retain shape well
found in: structures that are frequently stretched (vocal chords)
AKA: yellow fibers
3. reticular fibers: very thin collagenous fibers
highly branched
function: form delicate supporting networks
IV. Loose connective tissue: AKA areolar tissue
contain large numbers of fibroblasts, matrix is gel-like
matrix contains collagenous and elastic fibers
function: form delicate, thin membranes in the body
found in: membrane that connects skin to underlying tissues
(fascia), also found in spaces between muscles
found deep to most epithelial tissues, contains many
blood vessels
V. Adipose tissue: AKA fat
function: long-term energy storage, cushioning, insulation
formed when: cells store fat in droplets in cytoplasm & enlarge
found: under skin, covering many internal organs, spaces
between muscles, behind the eyes, around some joints
VI. Dense connective tissue:
thick, tightly spaced fibers (mostly collagenous and elastic),
very few cells (fibroblasts)
very strong, can withstand strong pulling forces
found in: tendons, ligaments, white part of eye (sclera),
deep skin layers
VII. Cartilage:
rigid connective tissue, cells are called chondrocytes,
form framework for body parts
not many blood vessels, heal slowly
perichondrium (covering of cartilage, has blood vessels)
1. hyaline cartilage: most common, glassy appearance, white,
matrix has fine collagenous fibers,
found: ends of bones, end of nose, rings in resp passages
framework for developing bones
2. elastic cartilage: dense network of elastic fibers
found: external ear, parts of larynx
3. fibrocartilage: very tough, many collagenous fibers,
serves as a shock absorber
found: knees, pelvic girdle, vertebral discs
VIII. Bone:
-most rigid connective tissue type
-hardness of bone is due to calcium salts (Ca phosphate, Ca carbonate)
between the cells
-matrix contains lots of collagen (gives flexibility & reinforces bone)
functions: support of body structures, attachment point for muscles,
protection of internal structures, production of blood cells,
storage and release of calcium and phosphate
IX. Blood:
-only connective tissue that is in constant motion
-composed of formed elements (cells) which are suspended in a liquid
matrix (plasma)
cell types: red blood cells, white blood cells, platelets
plasma contains: coagulation factors, enzymes, nutrients, water
functions: distribution of hormones, gas exchange, delivery of
nutrients, removal of waste products, distribution of body
heat, protection against infection, repair of injury