The Tissue Level of Organization Chapter 3

Tissue Definition – an aggregation of cells in which each cooperates with all others in the performance of a given function Examples of general functions –Movement –Protection –Support –Production of chemicals

Principal Tissue Types Epithelial Connective Muscular Nervous

Human Anatomy, 3rd edition Prentice Hall, © 2001 Epithelial Tissue Functions –Coverings and linings –Forms glands Characteristics –Closely packed cells –Basement membrane –Nerves –Avascular –Cell growth and replacement by mitosis Classification –Simple or stratified –Squamous, cuboidal, columnar, or transitional

Epithelia of Coverings and Linings

Human Anatomy, 3rd edition Prentice Hall, © 2001 Squamous Epithelium Simple Squamous Epithelium –Highly adapted to diffusion, osmosis, & filtration Stratified Squamous Epithelium –Surface layer is flat –Function - protection

Human Anatomy, 3rd edition Prentice Hall, © 2001 Cuboidal Epithelium Simple cuboidal epithelium Lines glands and their ducts Function – secretion and absorption Stratified Cuboidal epithelium –Surface layer cube-shaped –Function – protection

Transitional Epithelium Can be stretched Lines hollow structures that expand Function – prevents rupture of organ

Human Anatomy, 3rd edition Prentice Hall, © 2001 Columnar Epithelia Simple columnar epithelium –Functions – protection, absorption, secretion Stratified columnar epithelium –Surface layer is column-shaped –Function – protection

Pseudostratified Columnar Epithelium Appear stratified but all cells connect to the basal lamina Functions – protection, secretion

Glandular Epithelium Gland – 1 or more cells –Unicellular gland – goblet cell –Multicellular – secretory sheets or groups of cells Serous Mucous Mixed Function – secretion Types –Exocrine – to surface or ducts –Endocrine – to blood

Human Anatomy, 3rd edition Prentice Hall, © 2001 Mechanisms of Glandular Secretion Merocrine –Secretion is released by exocytosis Apocrine –Secretion is released by pinching off of vesicles Holocrine –Secretion is released by entire cell bursting

Connective Tissue Most abundant tissue Functions are varied Characteristics –Specialized cells, widely scattered –Rich blood supply –Much matrix Extracellular fibers Ground substance

Human Anatomy, 3rd edition Prentice Hall, © 2001 Classification of Connective Tissues Embryonic –Mesenchymal cells Adult connective tissues

Human Anatomy, 3rd edition Prentice Hall, © 2001 Embryonic Connective Tissues

Cell Types Found in Connective Tissue Fibroblasts –Secrete the molecules that form the matrix –Fixed cells Fibrocytes Macrophages –“Big eaters” –May be fixed or wandering

Additional Connective Tissue Cells Adipocytes –Fixed fat cells Mesenchymal cells –Fixed cells that can divide (mitosis) to replace damaged connective tissue Melanocytes –Fixed cells that store melanin Lymphocytes –Wandering immune system cells Mast cells –Around blood vessels –Wandering cells that produce histamine & heparin

Connective Tissue Fibers Collagen fibers –Most common type –White –Strong, ropelike –Form ligaments, tendons Reticular fibers –Thin –Woven into rough, flexible network Elastic fibers –Yellow –Thin –Stretch Contain elastin

Ground Substance Extracellular fluid in connective tissue –Water –Glycoproteins

Types of Connective Tissue

Human Anatomy, 3rd edition Prentice Hall, © 2001 Loose (Areolar) Connective Tissue Fibers not abundant Contains all 3 types of fibers Examples of locations –Between skin and muscles –Around digestive tract –Around blood vessels

Human Anatomy, 3rd edition Prentice Hall, © 2001 Adipose Tissue Most of the volume is adipocytes Provides padding, slows heat loss, food reserve Locations –Wherever there is loose connective tissue

Human Anatomy, 3rd edition Prentice Hall, © 2001 Reticular Tissue Reticular fibers form a strong network Provides strength and support Forms the framework (stroma) of many organs Binds together cells of smooth muscle

Dense Connective Tissue Types –Dense Regular Connective Tissue –Dense Irregular Connective Tissue –Elastic Connective Tissue

Human Anatomy, 3rd edition Prentice Hall, © 2001 Dense Regular Connective Tissue Lots of collagen fibers in bundles Cells – fibroblasts in rows between bundles Examples –Tendons, ligaments

Human Anatomy, 3rd edition Prentice Hall, © 2001 Dense Irregular Connective Tissue Tensions in various directions Occurs in sheets Locations –Periosteum –Perichondrium –Fibrous capsules of some organs –Fasciae –Dermis

Human Anatomy, 3rd edition Prentice Hall, © 2001 Elastic Tissue Lots of elastic fibers Fibroblasts in spaces between fibers Provides stretch and strength

Cartilage Dense network of collagenous fibers & elastic fibers in a gel-like substance Cells – chondrocytes in lacunae –Chondroblasts Perichondrium – surrounds surface of cartilage Growth –Interstitial growth –Appositional growth

Growth of Cartilage

Types of Cartilage Hyaline cartilage Fibrocartilage Elastic cartilage

Human Anatomy, 3rd edition Prentice Hall, © 2001 Hyaline Cartilage Most common Provides flexibility and support Locations –Ends of bones –Trachea –Larynx –Embryonic skeleton

Human Anatomy, 3rd edition Prentice Hall, © 2001 Fibrocartilage Visible collagenous fibers with scattered chondrocytes Provides strength and rigidity Locations –Intervertebral discs –Symphysis pubis

Human Anatomy, 3rd edition Prentice Hall, © 2001 Elastic Cartilage Threadlike network of elastic fibers with chondrocytes Provides strength and maintains shape Locations –Pinna –Eustacian tube

Human Anatomy, 3rd edition Prentice Hall, © 2001 Bone Solid matrix Cells –Osteocytes in lacunae –Osteoblasts –Osteoclasts Periosteum surrounds surface of bone

Human Anatomy, 3rd edition Prentice Hall, © 2001 Blood Functions –Transport medium –Regulation –Protection Composition –Plasma – fluid –Formed elements – cells & cell fragments Erythrocyte Leukocyte Thrombocyte

Human Anatomy, 3rd edition Prentice Hall, © 2001 A Red Blood Cell

Human Anatomy, 3rd edition Prentice Hall, © 2001 SEM of RBCs

Human Anatomy, 3rd edition Prentice Hall, © 2001 Membranes Epithelial layer + underlying connective tissue = epithelial membrane Types –Mucous membrane –Serous membrane –Cutaneous membrane –Synovial membrane

Fascia Fascia – collective term for sheets of connective tissue Functions –Provide strength and stability –Maintain positions of internal organs –Provide a route for the distribution of blood vessels, lymphatics, and nerves 3 types

Human Anatomy, 3rd edition Prentice Hall, © 2001 Types of Fascia Superficial Fascia –Adipose tissue and loose connective tissue –Immediately deep to the skin Deep Fascia –Dense connective tissue –Strong internal framework Subserous Fascia –Loose connective tissue –Between deep fascia and serous membranes

Muscular Tissue Specialized cells Function - contraction 3 types –Skeletal muscle –Cardiac muscle –Smooth muscle

Human Anatomy, 3rd edition Prentice Hall, © 2001 Skeletal Muscle Connected to bones Striated Multinucleated Voluntary

Human Anatomy, 3rd edition Prentice Hall, © 2001 Cardiac Muscle Found in the heart Striations Intercalated discs Involuntary

Human Anatomy, 3rd edition Prentice Hall, © 2001 Smooth Muscle Found in walls of internal organs Nonstriated Involuntary

Human Anatomy, 3rd edition Prentice Hall, © 2001 Nervous Tissue Specialized cells Function – conduction of electrical impulses Cells –Neurons –Neuroglia