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Tissues
Four major tissue types
1.
2.
3.
4.
Epithelial
Connective
Muscle
Nervous
1 - Epithelial Tissues
General characteristics • cover organs and the body
• line body cavities
• line hollow organs
• avascular
• cells readily divide
• cells tightly packed
• function in protection, secretion, absorption, and excretion
• classified according to cell shape and number of cell layers
Epithelial Tissues
1. Simple squamous –
• single layer of flat cells
• substances pass easily through
• line air sacs
• line blood vessels
• line lymphatic vessels
2. Simple cuboidal –
• single layer of cube-shaped
cells
• line kidney tubules & ducts of
some glands
• cover ovaries
Epithelial Tissues
3. Simple columnar –
• single layer of elongated cells
• sometimes possess cilia or microvilli
• line uterus, stomach, intestines
4. Pseudostratified columnar –
• single layer of elongated cells
• appear striated
• often have cilia
• line respiratory passageways
Epithelial Tissues
5. Stratified squamous –
• many cell layers
• top cells are flat
• can accumulate keratin
• outer layer of skin
• line oral cavity, throat, vagina,
and anal canal
6. Stratified cuboidal –
• 2-3 layers
• cube-shaped cells
• line ducts of mammary, sweat
& salivary glands, and the
pancreas
Epithelial Tissues
7. Stratified columnar –
• top layer of elongated cells
• cube-shaped cells in deeper
layers
• line vas deferens, male
urethra, and part of
pharynx
8. Transitional –
• many cell layers
• cube-shaped and elongated
cells
• line urinary bladder,
ureters, and part of urethra
Glandular Epithelium
Composed of cells that are specialized to produce and secrete
substances.
1. Endocrine glands are ductless (product secreted into tissue
fluid or blood)
2. Exocrine glands have ducts (product secreted into ducts)
- Unicellular exocrine gland
• composed of one cell
• goblet cell (secrete mucous)
- Multicellular exocrine gland
• composed of many cells
• sweat glands, salivary glands, etc.
Types of Glandular Secretions
1. Merocrine glands 2. Apocrine glands
• fluid product
(exocytosis)
• salivary/sweat
glands
• pancreas
• cellular product
• lose portions of cells
• mammary glands
3. Holocrine glands
• secretory products
• release whole cells
• sebaceous glands
2 - Connective Tissues
General characteristics • most abundant tissue type
• many functions
• bind structures
• provide support and protection
• serve as frameworks
• fill spaces
• store fat
• produce blood cells
• protect against infections
• help repair tissue damage
• have a matrix (cells are farther apart than epithelial)
• have varying degrees of vascularity
• have cells that usually divide
• some are quite rigid (bone and cartilage), some are more
flexible (adipose tissue)
Connective Tissue
Major Cell Types
1. Fibroblasts
• fixed cell (present in
stable numbers)
• most common cell
• large, star-shaped
• produce fibers
3. Macrophages
• wandering cell (appear
temporarily)
• phagocytic
• important in defense
2. Mast cells
• fixed cell
• release heparin (anticoagulant)
• release histamine (chemical messenger, causes
vasodilation)
Connective Tissue Fibers
1. Collagenous fibers
• thick
• composed of collagen
• great tensile strength
• abundant in dense CT
• hold structures together
• tendons, ligaments
3. Elastic fibers
• bundles of microfibrils
embedded in elastin
• elastic
• vocal cords, air passages
2. Reticular fibers
• very thin collagenous fibers
• highly branched
• form supportive networks
Connective Tissues
I- Connective tissue proper
II- Specialized connective tissue
1. loose connective tissue
6. bone
2. adipose tissue
7. cartilage
3. reticular connective tissue
8. blood
4. dense connective tissue
5. elastic connective tissue
Connective Tissues
1. Loose connective tissue
• mainly
fibroblasts
• fluid to gel-like matrix
• collagenous fibers
• elastic fibers
• bind skin to structures
• beneath most epithelia
• between muscles
2. Adipose tissue
• adipocytes
• cushions and insulates
• stores fats
• beneath skin
• behind eyes
• around kidneys and
heart
Connective Tissues
3. Reticular connective tissue
• composed
of reticular
fibers
• supports
• walls of liver, spleen,
lymphatic organs
4. Dense connective tissue
• packed
with
collagenous fibers
• elastic fibers
• few fibroblasts
• bind body parts
together
• tendons, ligaments,
dermis
• poor blood supply
Connective Tissues
5. Elastic connective tissue
• abundant
in elastic fibers
• some collagenous fibers
• fibroblasts
• attachments between
vertebrae
• walls of large arteries,
airways, heart
6. Bone
• solid matrix
• supports and protects
• forms blood cells
• attachment for muscles
• skeleton
• osteocytes in lacunae
Connective Tissues
7. Cartilage
• rigid
matrix
• chondrocytes in
lacunae
• poor blood supply
• three types
a. hyaline
b. elastic
c. fibrocartilage
a. Hyaline cartilage
• most abundant
• ends of bones
• nose, respiratory passages
• embryonic skeleton
b. Elastic cartilage
• flexible
• external ear, larynx
c. Fibrocartilage
• very tough
• shock absorber
• intervertebral discs
• pads of knee and pelvic girdle
Connective Tissues
Three types of cartilage
Connective Tissues
8. Blood
• fluid matrix called
plasma
• contains red and white
blood cells, as well as
platelets
•transports/defends/
clotting
• throughout body in
blood vessels
• heart
3 - Muscle Tissues
General characteristics
• muscle
cells called
muscle fibers
• contractile
• three types
1. skeletal
2. smooth
3. cardiac
1. Skeletal muscle
• attached to bones
• striated
• voluntary
2. Smooth muscle
• walls of organs
• skin
• walls of blood vessels
• involuntary
• not striated
3. Cardiac muscle
• heart wall
• involuntary
• striated
Muscle Tissues
4 - Nervous Tissues
• found in brain, spinal cord, and
peripheral nerves
• basic cells are neurons
• neuroglial cells are supporting
cells
• sensory reception
• conduction of nerve impulses