The Tissue Level of Organization The Tissue Level of Organization 4 4

Overview of Tissue Science Histology: The study of tissues Four Basic Tissue Types Epithelial Connective Muscular Neural

Overview of Tissue Science Key Notes: Tissues are collections of cells and extracellular material that perform a specific but limited range of functions. The four tissue types, in varying combinations, form all of the structures of the human body.

Overview of Tissues

Epithelial Tissue - Includes epithelia & glands Epithelia: - layers of cells that cover internal and external surfaces Glands: - composed of secreting cells derived from epithelia

Important Characteristics of Epithelia Cells are closely packed together A free(Apical) surface is exposed to the environment or to internal cavities Cells are attached to a basement membrane Lacks blood vessels(avascular) Cells are continually replaced & regenerated

Functions of Epithelia Physical protection Permeability control Sensation trigger Specialized secretions

Gland Cells Gland cells produce secretions Two Classes of Glandular Secretion: Exocrine secretion- Secretion onto a body surface Ex: digestive enzymes in digestive tract, perspiration on skin Endocrine secretion- Secretion (of hormones) into neighboring tissues and blood Ex: pancreas, thyroid, pituitary gland

Intercellular Connections Epithelial cells are firmly attached to the basement membrane and to one another Epithelial cells are held together by CAMs(cell adhesion molecules) and a thin layer of intercellular cement Cell junctions: attachment sites between cells Tight junctions- many attachments between cells using membrane proteins Gap junctions- several attachments between cells using transport proteins Desmosomes- attachment between cells using CAMs

Intercellular Connections

The Epithelial Surface The apical surface of epithelial cells has specialized structures Microvilli: Abundant on transport cells Dramatically increase surface area Found in intestinal lining, kidney tubules Cilia: Beat in coordinated fashion Move fluid along surface Found in airways, oviduct

The Surfaces of Epithelial Cells

The Basement Membrane The basement membrane is an area between the epithelium and connective tissue - Provides strength and helps in resisting distortion - Prevents proteins & large molecules from entering the epithelium

Classifying Epithelia Epithelium cells are classified by the # of layers and shape of cells Number of layers Simple (one cell thick) Stratified (multiple cells thick) Cell shape Squamous (flat) Cuboidal (cubic) Columnar (tall columns)

Epithelial Tissue

Cell Layers Simple Epithelium: - a single layer of cells covering basement membrane - line internal compartments and passageways - found where secretion and absorption occurs Ex: lungs, digestive tract, urinary tract

Cell Layers Stratified Epithelium: - provides greater protection from several layers of cells - found in areas of chemical and physical stress Ex: surface of skin, mouth, anus

Epithelial Tissue Simple Squamous Epithelium

Epithelial Tissue Simple Cuboidal Epithelium

Epithelial Tissue Simple Columnar Epithelium

Epithelial Tissue Pseudostratified Ciliated Columnar

Epithelial Tissue Transitional Epithelium

Epithelial Tissue Stratified Squamous Epithelium

Glandular Epithelia Exocrine Glands: secrete products through ducts(tubes) onto an external or internal surface ex: salivary glands, mammary glands, sweat glands(sebaceous glands) Endocrine Glands: secrete hormones directly into the blood or tissue fluids ex: pituitary, thyroid Modes of Secretion: Merocrine- secretion via exocytosis Apocrine- shed a portion of the cell Holocrine- burst of entire cell contents

Mechanisms of Glandular Secretion Figure 4-6

Connective Tissues -Connective tissues are the most diverse tissue in the body in form and function Connective Tissues Components: Specialized cells Extracellular matrix(protein fibers) Ground Substance Fluid

Functions of Connective Tissue Structural framework Fluid and solute transport Physical protection Tissue interconnection Fat storage Microorganism defense

Classifying Connective Tissues Connective Tissue Proper- tendons, ligaments, and fatty tissue Fluid Connective Tissues- blood & lymph Supporting Connective Tissues- cartilage & bone

Connective Tissues Major Types of Connective Tissue

Connective Tissue Proper Components: Fibroblasts- produce and maintain connective tissue Macrophages- engulf damaged cells or pathogens in tissues Fat Cells(adipocytes)- store fluids & fatty acids Mast Cells- release chemicals to initiate the immune system after an injury or infection

Connective Tissue Fibers Collagen fibers- long, straight, unbranched, strong & flexible Reticular fibers- thin fibers that form an interwoven framework in various organs Elastic fibers- contain elastin protein, are branched and waving, will return to their original length after stretching

Cells and Fibers of Connective Tissue Proper

Types of Connective Tissue Loose Connective Tissue: - least specialized type of connective tissue - forms a layer that separates the skin from underlying muscles - provides padding and allows for muscle movement Adipose Tissue(fat): - loose connective tissue containing large #’s of fat cells Dense Connective Tissue: - consists mostly of collagen fibers Tendons- cords of dense connective tissue connecting muscle to bone Ligaments- connect bone to bone, can stretch a little

Connective Tissues Loose Connective Tissue

Connective Tissues Adipose Tissue

Connective Tissues Dense Connective Tissues

Fluid Connective Tissues Blood: the watery matrix in blood is called plasma Plasma- contains RBC’s, WBC’s, platelets, proteins, carbs. & fats RBC’s- make up 50% of blood volume - carry oxygen from lungs to cells WBC’s- support the immune system Platelets- function in blood clotting

Supporting Connective Tissue -Provides a framework that supports the rest of the body Cartilage: a firm gel containing embedded fibers Condrocytes- cells found in cartilage matrix * there are no blood vessels in cartilage Perichondrium- covering on outer surface of cartilage

Cartilage Types of Cartilage: Hyaline Cartilage- found in joints Elastic Cartilage- ear Fibrocartilage- between vertebrae

Connective Tissues Hyaline Cartilage

Connective Tissues Elastic Cartilage

Connective Tissues Fibrocartilage

Bone (Osseous Tissue) Bone is composed of hard calcium deposits & collagen fibers Osteocytes- bone cells Canaliculi- canals in bone that transmit nutrients Periostenum- outer covering of bone

Connective Tissues Bone

Membranes Properties of Membranes Barrier or interface that separate epithelial and connective tissue Cover and protect organs

Membranes Types of Membranes Mucous Lines cavities that connect to exterior Mucus moistens surface Examples: oral cavity, airways Serous Line internal cavities Watery fluid moistens surface Example: peritoneal membrane

Membranes Types of Membranes (continued) Cutaneous Covers body surface Dry surface waterproofs the body Example: the skin Synovial Lines joints Secretes slippery synovial fluid Lubricates joints Examples: knee, elbow

Membranes

Muscle Tissue Properties of Muscle Tissue Capable of contraction Contraction involves interaction between filaments of actin and myosin found in the cytoskeleton of muscle cells Three types of muscle tissue: Skeletal muscle Cardiac muscle Smooth muscle

Muscle Tissue Skeletal Muscle Tissue Contains elongated cells (fibers) Fibers tied together by loose connective tissue Possesses microscopic striations Contains many nuclei Controlled by voluntary nervous system Moves and stabilizes the skeleton

Muscle Tissue Skeletal Muscle Tissue

Muscle Tissue Cardiac Muscle Tissue Only in heart Short, branched fibers Single nucleus Striated(striped) Involuntary contraction Blood circulation Blood pressure

Muscle Tissue Cardiac Muscle Tissue

Muscle Tissue Smooth Muscle Tissue Short, tapering cells No striations Involuntary contraction Blood vessels Urinary bladder Digestive organs Uterus

Muscle Tissue Smooth Muscle Tissue

Neural Tissue Properties of Neural Tissue Conduct electrical impulses Transfer, process, and store information Comprises neurons and neuroglia Concentrated in the brain and spinal cord

Neural Tissue Neurons Dendrites Information entry Cell body Information integration Axon (nerve fibers) Information transmission Synaptic terminals Information transfer

Neural Tissue Neuroglia Several types of neuroglia Provide physical support Maintain extracellular chemistry Supply nutrients Defend against infection

Neural Tissue

Tissue Injuries and Repair An injury harms multiple tissues simultaneously Tissues make coordinated response Responses restore homeostasis Two response types Inflammation Restoration

Tissues and Aging Tissues Change with Age Healing slows Epithelia become thinner Connective tissues become more fragile Bones weaken, become brittle Neuron and muscle fiber losses accumulate Lifestyle interventions slow decline

Tissues and Aging Aging and Cancer Incidence Cancer risk rises with age After heart disease, cancer second leading cause of death Smoking linked to 40% of cancers 75% caused by environment

END OF CHAPTER 4 NOTES!!!