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

1. EPITHELIAL Covers and protects body surface Lines body cavities Secretes and absorbs substances into and out of blood Forms glands

2. CONNECTIVE Supports and connects body and its parts Transports substances throughout the body Protection from invading microbes Cells spread out; lots of matrix

3. MUSCLE Produces movement by shortening complex contractile proteins

4. 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)

Simple squamous

Simple squamous and simple cuboidal

Squamous cells at surface

Simple squamous (endothelial lining)

Simple cuboidal

Simple cuboidal of thyroid glands

Simple cuboidal

Simple columnar

Simple columnar

Pseudostratified

Pseudostratified

Cilia on apical surface of pseudostratified epithelial tissue

Transitional

Transitional; note dome shaped cells at apical surface

Nonkeratinized stratified squamous

Nonkeratinized stratified squamous epithelium

Keratinized stratified squamous epithelial tissue (skin)

Stratified cuboidal

Stratified columnar

CLASSIFICATION OF GLANDULAR EPITHELIUM Exocrine – discharge products into ducts 1. Apocrine 2. Holocrine 3. Merocrine Endocrine – ductless glands

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

B. ADIPOSE Mostly fat cells (adipocytes) Protection, insulation, energy storage

Adipose

C. RETICULAR 3-D web Defense; reticular network filters harmful substances from lymph and blood Reticular cells phagocytic

Reticular

D. DENSE REGULAR Mainly bundles of collagen arranged in parallel rows Few fibroblasts Ligaments (bone to bone) and tendons (muscle to bone)

Dense regular

E. DENSE IRREGULAR Bundles of collagen arranged in various planes Dermis of the skin Joint capsules

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

F. HYALINE CARTILAGE Shiny Most prevalent type Support tubes of respiratory system, ribs, tip of nose, ends of bones

Hyaline cartilage

Note glassy appearance of matrix

G. ELASTIC More elastic fibers Strong and flexible External ear, epiglottis

Elastic cartilage

Note elastin fibers in matrix

H. FIBROCARTILAGE Strongest Shock absorbers Found between vertebrae and knee joints Rigid matrix filled with strong white fibers

Fibrocartilage

I. BONE Osteocytes in matrix of collagen and mineral salts (65%) Support, protection, muscle attachment; mineral storage; hemopoiesis Haversian system

Bone

Compact bone; note lacunae, canaliculi

Osteons; note lamellae (circumferential and interstitial)

J. BLOOD Liquid matrix (plasma) Fibers only present at clotting Erythrocytes, leukocytes and platelets are the cells

Blood

III. MUSCLE A. Skeletal B. Cardiac C. Smooth Multinucleate, cross striations B. Cardiac Heart wall; cross striations, intercalated disks, involuntary Visceral C. Smooth involuntary, one nucleus per cell, non striated

Skeletal muscle

Cardiac muscle

Smooth muscle

Smooth muscle

IV. NERVOUS Nerve cells Neuroglia Neurons Cell body (soma), axons (away) dendrites (toward cell body) Neuroglia Connecting and supporting cells

IV. Nerve

Neuron smear; small dots are nuclei of glial cells (neuroglia)

Peripheral nerve in cross section