HISTOLOGY

THE STUDY OF TISSUES

TISSUES• Organization of similar cells

embedded in a matrix (nonliving, intercellular material

• Matrix can be rigid, gel, fluid or nonexistent

• Specialize in performing at least one unique function essential for life

I. EPITHELIAL

• Covers and protects body surface• Lines body cavities• Secretes and absorbs substances

into and out of blood• Forms glands

II. CONNECTIVE• Supports and connects body and

its parts• Transports substances throughout

the body• Protection from invading microbes• Cells spread out; lots of matrix

III. MUSCLE

• Produces movement by shortening complex contractile proteins

IV. NERVOUS

• Communication between body parts and integration of their activities

1. EPITHELIAL• 2 types:

1. Membranous – covers and lines body

2. Glandular – exocrine and endocrine

FUNCTIONS• Protection• Secretion• Absorption• Excretion• Sensory

CHARACTERISTICS• Limited amount of matrix• Basement membrane• Avascular• Held together by fused cell

membranes• Reproduce by mitosis• Nutrients by diffusion• Polarity

CLASSIFICATION OF MEMBRANOUS EPITHELIUM

• Based upon cell shape– Squamous (flat), cuboidal, or

columnar• Based upon # of cell layers

– Simple (single) or stratified (layered)

Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn

Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.

Figure 4.1: Classification of epithelia, p. 120.

Stratified

Simple

Apical surface

Basal surface

Apical surface

Basal surface

Squamous

Cuboidal

Columnar(a) (b)

Simple squamous

Simple cuboidal

Simple columnar

Pseudostratified

Transitional

Nonkeratinized stratified squamous

II. CONNECTIVE• Most abundant and diverse• Connects, supports, transports and

defends• Few cells, mostly matrix (nonliving

extracellular material); various numbers and kinds of fibers

1. AREOLAR• Most common and widely

distributed• Matrix is soft gel – hyaluronic acid• Matrix = collagen and elastin

fibers• Fibroblasts (secrete matrix) are the

predominant cells• Macrophages (phagocytosis)• Mast cells – secrete histamine

Areolar

2. ADIPOSE

• Mostly fat cells (adipocytes)

• Protection, insulation, energy storage

Adipose

3. RETICULAR• 3-D web• Defense; reticular network filters

harmful substances from lymph and blood

• Reticular cells phagocytic

Reticular

4. DENSE REGULAR• Mainly bundles of collagen

arranged in parallel rows• Few fibroblasts• Ligaments (bone to bone) and

tendons (muscle to bone)

Dense regular

5. DENSE IRREGULAR• Dermis of the skin

Dense irregular

6. CARTILAGE• One cell type: chondrocyte• Chondrocytes produce fibers and

tough gristlike material (chondroitin sulfate)

• Avascular – nutrients diffuse through perichondrium which surrounds cartilage mass

A. HYALINE CARTILAGE• Shiny• Most prevalent type• Support tubes of respiratory

system, ribs, ends of long bones that articulate at joints

Hyaline cartilage

B. ELASTIC

• Strong and flexible• External ear, epiglottis, larynx

Elastic cartilage

C. FIBROCARTILAGE• Strongest• Shock absorbers• Found between vertebrae and

knee joints• Rigid matrix filled with strong

white fibers

Fibrocartilage

7. BONE• Osteocytes in matrix of collagen

and mineral salts (65%)• Support, protection, muscle

attachment; mineral storage; hemopoiesis

• Haversian system

Bone

8. BLOOD• Liquid matrix• Fibers only present at clotting• Plasma = 55%• Erythrocytes, leukocytes and

platelets are the cells

Blood

III. MUSCLE• 1. Skeletal

– Multinucleate, cross striations• 2. Cardiac

– Heart wall; cross striations, intercalated disks, involuntary Visceral

• 3. Smooth– involuntary, one nucleus per cell, non

striated

Skeletal muscle

Cardiac muscle

Smooth muscle

IV. NERVOUS• Nerve cells

– Neurons • Cell body (soma), axons (away) dendrites

(toward cell body)• Neuroglia

– Connecting and supporting cells

IV. Nerve