TISSUE ORGANIZATION

Histology - is the study of tissues

EMBRYONIC GERM LAYERS

Ectoderm - epidermis of the skin,nervous system

Endoderm - functional lining of the digestive, respiratory tract; accessory organs and glands such as lungs, stomach,pancreas

Mesoderm - skeletal system, muscular system, and circulatory system

MAIN TISSUE TYPES

EpithelialConnectiveMuscleNervous

EPITHELIAL TISSUE

Location–sheets or layers lining body

tubes, cavities, or covering body surfaces

–Form many glands

GENERAL CHARACTERISTICS

Form sheets, layers Cells fit together tightly One edge attached to basement membrane No blood supply Regenerate quickly Many are secretory Supported by connective tissue

FUNCTIONS

ProtectionAbsorptionFiltrationSecretionGas exchange

EPITHELIAL TISSUE TYPES

Number of layers– simple epithelium

– stratified epithelium

– pseudostratified epithelium

Shape of cells– squamous (flat)

– cuboidal ( cubed)

– columnar ( tall)

– transitional (varies)

Examples of Epithelial Tisuue

Simple squamous Simple cuboidal Simple columnar Simple columnar

– ciliated

Pseudostratified columnar

Stratified squamous– keratinized

– non-keratinized

Stratified cuboidal Stratified columnar Transitional Glandular

endocrine (ductless) - secrete hormones into blood exocrine- secrete through ducts to specific

locations

• unicellular - “goblet cells”

• multicellular

–modes of secretion

»apocrine - apex pinches off

»holocrine - accumulate until rupture

»merocrine -most common;secrete by exocytosis

Glandular Epithelial Tissue Types

CONNECTIVE TISSUE

Most abundant and widespread tissue found in the body

GENERAL CHARACTERISTICS Many types with great diversity Very good blood supply Cells usually spaced apart from each other Intercellular material (matrix) separating cells No free surface Derived from mesenchyme Consist of ground substance, fibers, cells

Connective Tissue Functions

Physical protection Support Binding Absorb shock Insulation Stores energy Blood production Immunity

Types of Fibers

Collagen - very tough and strong – contains collagen protein

Elastic - very flexible and stretchable– contains elastin protein

Reticular - forms network mesh– contains collagen & glycoprotein

Types of Cells Fibroblast - “fiber-

forming cells” Macrophage - “big

eaters” phagocytic white blood cells

Mast cell - sentry cells; detect foreign substances; produce inflammatory chemicals– heparin; histamine

Plasma cells - produce antibodies

WBC - neutrophils, basophils, eosinophils, lymphocytes, monocytes

Adipose - store fat

Connective Tissue Proper

Loose Connective(Areolar) - attaches skin to underlying body parts; superficial fascia

Adipose - energy storage; insulation

Reticular - binds smooth muscles together

Regular dense connective tissue(fibrous)– tendon; ligaments

Irregular dense– fascia, periosteum

Elastic connective– blood vessels, lung tissue

Cartilage

Hyaline cartilage (gristle)– ends of long bone, nose tip, connects ribs to

sternum Elastic cartilage

– external ear Fibrocartilage

– between pubic symphysis– discs between vertebrae

OSSEOUS TISSUE - BONE

MATRIX

30% collagen fibers

70% mineral salts

Osseous Tissue

Types of Cells– osteocytes

– osteoblasts

– osteoclastsTypes of Bone

– Cancellous (Spongy) Bone - trabeculae

– Compact Bone - Haversian Canal System

Blood Tissue (Vascular)

Hemopoietic Tissue (blood forming tissue)

Types of Cells: – erythrocytes (RBC’s)

– leukocytes (WBC’s)

– platelets (thrombocytes)

MUSCLE TISSUE

Contractile tissue

Responsible for movement

Skeletal Muscle - Voluntary

Long, threadlike cells with parallel fibers

Cells are multinucleate with nuclei located peripherally; striated

Usually attached to long bones

Smooth Muscle - Involuntary

Spindle shaped cells with single nucleus per cell

No striations Located in blood vessels, walls of hollow

organs, and the gastrointestinal tract

Cardiac Muscle - Involuntary

Branched cells with striated fibersIntercalated discsOnly a single nucleus per cellOnly found in the heart

NERVE TISSUE

Characterized by the ability to conduct electrical signals

Nervous Tissue

Located in the brain and spinal cord (CNS) and in the nerves (PNS)

Sensitive to changes in the internal and external environment

Conducts nerve impulses to other neurons/body parts

NERVE TISSUE

Functions in coordinating, regulating, and integrating body activities

Types of Cells: – neuroglial cells - support cells

– neuron - cell body, axon, dendrites

MEMBRANES

Thin sheet or layer of tissue that covers a structure or lines a

cavity

Epithelial Membranes

Cutaneous membrane - skinSerous membrane - (serosa)

– found in closed cavities• parietal membrane - lines inside of cavities

• visceral membrane - covers organs

Mucous membrane - mucosa – line cavities that open to the exterior

Connective Tissue Membranes

Synovial Membrane–line spaces between bones in joints

–secrete synovial fluid