Chapter 4 - Tissues Histology: the study of tissues 1. Tissue:

cells performing one job communication through chemical or electrical means can include extracellular fluids or materials (blood, bone)

List of tissues:

a) epithelial c) muscular

b) connective d) nervous

2. Extracellular fluid (ECF) vs. Intracellular fluid (ICF) Percentage in body

ICF - inside cells ECF – outside cells -Plasma -Interstitial fluid

3. Epithelial tissue

a) general characteristics

Locations in body:

-lining body cavities (parietal) -covering organs (visceral) -glands - body surfaces -often a flat sheet of cells attached to basement membrane. -avascular (

Functions:

-protection, secretion, absorption

b) two criteria for naming epithelial tissue:

i) number of cell layers

simple one cell layer

stratified – 2 or more cells thick

ii) cell shape

squamous flat, pancake-like

cuboidal – cube shaped

columnar – tall rectangular

i) simple squamous iv) stratified squamous

ii) simple cuboidal v) stratified cuboidal

iii) simple columnar vi) stratified columnar

c) two “oddball” epithelial tissues:

i) pseudostratified columnar

Looks stratified, but simple. Nuclei offset Often ciliated.

ii) transitional

stratified & all 3 cell shapes able to stretch and return to original shape

4. Connective tissue

-most widely distributed tissue -connects other tissues.

a) ground substance

non-living & structureless environment which cells live watery to solid (blood) (bone)

b) protein fibers: non-living proteins secreted by cells

i) collagen string, rope-like tough

ii) reticular short, net-like, branched

iii) elastic stretchable, ions, small diameter

c) cells (3 types)

1. Fibroblast – secretes all 3 fibers 2. Macrophage – a specialized WBC (phagocytosis) 3. Mast cell – produces histamine ( ) and

heaparin ( ).

5) loose connective tissues: a family group of tissues - a fluid matrix - a loose or open pattern of fibers & cells -relatively high % of cells in tissue.

a. areolar- -many cell types. All 3 protein fibers. Found throughout body.

*Loose packing and protection

b) adipose = FAT - contains adipocyte (cell that stores extra lipids) - contain reticular fibers -*protectection of organs, insulation and energy storage

c) reticular

-contains many reticular fibers - binds smooth muscle cells together * forms outer protective layer around organs (spleen)

6) dense connective tissues: -solid matrix -fibers and cells densely packed in ground substance -low percentage of cells in tissues. -3 types listed below:

i. dense regular

high concentration of collagen fibers – parallel arrangement -gives strength in one direction (tendons & ligaments)

b) dense irregular High concetration of collagen fibers – randomly oriented -gives strength in many directions (dermis)

c) elastic High concentration of elastic fibers allows tissue to stretch (vocal cords)

7) cartilage and bone ( we will discuss in skeletal system)

8) blood –(we will discuss in cardiovascular system)

9) bone marrow- (we will discuss in cardiovascular system)

10. muscular tissue – moves skeleton, movement of internal structures, pumps blood

1. skeletal – attaches to and moves skeleton *voluntary, multinucleate, non-striated

b. smooth movement of internal organs/ structures involuntary, uninucleate, non-striated

j) cardiac found only in heart involuntary, uninucleate, striated

11. nervous tissue (neurons and neuroglia) cells capable of sending and receiving electrochemical messages (action potentials) *regulation of many body functions. (thought, memory, personality etc.)

a) neurons

send and receive action potentials

b) neuroglia helper cells of neurons do not send and receive action potentials about 10-5- times more numerous than neurons.

1) astrocytes - form blood/brain barrier. Regulates chemicals, supports neurons. Isolates CNS from harmful substances in blood

2) oligodendrocytes – forms and maintains myelin sheath on

axon

3) ependymal cells -forms lining of cranial and vertebral cavities. Helps monitor and circulate fluid in cavity.

4) microglia -phagocytosis of bacteria/viruses & damaged nervous tissue

5) Schwann cells- forms myelin sheath on axon or can

bundle axons that have no myelin sheath.