Chapter 4 Tissue: The Living Fabric

Tissue: a group of closely associated cells working toward

a common goal

I. Epithelial tissue A. Two types

1. Covering and lining: on free surfaces of body

2. Glandular: forms glands of body

B. Special characteristics 1. Cellularity: consists of closely packed cells 2. Specialized contacts: cells fit together to form sheets 3. Polarity: possesses two different surfaces

a. Apical surface: upper (free) exposed surface b. Basal surface: lower attached surface

4. Supported by connective tissue 5. Avascular but innervated

6. Regeneration: high rate of cell division C. Classification of epithelia: by shape of the cell and the number of cell

layers 1. Classification by cell shape: 3 basic forms

a. Squamous: thin and flat

b. Cuboidal: shaped like tiny sugar cubes

c. Columnar: shaped like tiny columns

2. Classification by number of layers a. Simple epithelia: single layer - filtration and absorption areas

1) Simple squamous

2) Simple cuboidal

3) Simple columnar

a) Characteristics unique to columnar epithelium (1) Goblet cells: (2) Microvilli:

(3) Cilia:

b) Pseudostratified columnar

b. Stratified epithelia: two or more layers of cells – named for the shape of the outer rows 1) Stratified squamous: protective areas

a) Example areas (1) Tongue (2) Mouth (3) Pharynx (Throat)

b) Keratinized: contains keratin (1) Waterproofing protein (2) Skin only

2) Stratified cuboidal: rare: typically only 2 layers deep

3) Stratified columnar: Rare: a few rows at most

4) Transitional

3. Glandular epithelium: single or multi-cell structures that secrete a product a. Endocrine glands

1) Ductless 2) Produce hormones

b. Exocrine glands are the most common type

1) Unicellular: single cell glands

2) Multicellular: many cells a) All possess three components:

(1) Duct (2) Secretory unit

(3) Supportive connective tissue

b) Classification by the duct (1) Simple (2) Compound

c) Classification by secretory unit (1) Tubular: like tiny tubes

(2) Alveolar: grape-like clusters of secretory sacs

(3) Tubuloalveolar: both tubular and alveoli structure

d) Method of secretion (1) Merocrine: exocytosis

(2) Holocrine: ruptures cell

II. Connective tissue: the most common of all tissues

A. Common characteristics 1. Common origin: all arise from mesenchyme 2. Vascularity: varies from avascular to richly vascular 3. Matrix: few cells – mostly extracellular matrix

B. Structural elements of C.T: (3 main) 1. Ground substance: fills the space between cells

a. Interstitial fluid b. Cell adhesion proteins: connective tissue “glue”

2. Fibers provide support: three types of fibers

a. Collagen

b. Elastic

c. Reticular

3. Cells of C.T.

a. Fibroblast b. Chondroblast

c. Osteoblast d. Hemocytoblast e. Macrophages

C. Types of C.T. 1. Connective tissue proper: 2 divisions

a. Loose C.T.: 3 kinds 1) Areolar

2) Adipose

3) Reticular tissue

b. Dense C.T.: densely packed collagen and/or elastic fibers 1) If mostly collagen: high strength 2) If mostly Elastin: stretchy 3) Dense connective tissues have a poor blood supply 4) Three types:

a) Dense regular

b) Dense irregular

c) Elastic C.T.

2. Cartilage: avascular, no nerves, much extracellular material • Ground substance has many fibers for strength

• Chondroblasts produce the matrix and are called chondrocytes when completely surrounded by matrix

• Perichondrium is dense irregular C.T. covering cartilage (contains the blood and nerve supply)

a. Hyaline

b. Elastic cartilage

c. Fibrocartilage

3. Bone: supports and protects soft tissues

4. Blood: considered to be a C.T.

D. Epithelial membranes: possess both epithelium and C.T.

1. Cutaneous membrane a. Keratinized stratified squamous b. Connective tissue

2. Mucous membranes (mucosa)

a. Epithelium b. Connective tissue c. Function

3. Serous membranes a. Epithelium b. Connective tissue c. Function d. Parietal layer e. Visceral layer

III. Muscle Tissue A. Characteristics

1. Elongated shape 2. Myofibrils contain actin and myosin

B. 3 types of muscle tissue 1. Skeletal muscle: movement of the skeleton

2. Cardiac Muscle: the heart

3. Smooth Muscle: walls of hollow organs

IV. Nervous Tissue: brain, spinal cord, all peripheral nerves A. 2 major cell types:

1. Neurons: also called nerve cells – do not undergo mitosis 2. Neuroglia: supporting cells – undergo mitosis

a. Help support b. Protect c. Insulate