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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) Figure 4.1: Classification of epithelia, p. 120. Squamous Apical surface Cuboidal Basal surface Simple Apical surface Basal surface (a) Human Anatomy and Physiology, 7e by Elaine Marieb & Katja Hoehn Stratified Columnar (b) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Simple squamous Simple cuboidal Simple columnar Pseudostratified Transitional Nonkeratinized stratified squamous 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 • 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 long bones that articulate at joints Hyaline cartilage G. ELASTIC • Strong and flexible • External ear, epiglottis Elastic cartilage 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 J. BLOOD • • • • Liquid matrix Fibers only present at clotting Plasma = 55% Erythrocytes, leukocytes and platelets are the cells Blood III. MUSCLE • A. Skeletal – 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 IV. NERVOUS • Nerve cells – Neurons • Cell body (soma), axons (away) dendrites (toward cell body) • Neuroglia – Connecting and supporting cells IV. Nerve