Simple Squamous Epithelium

Description: single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the siples of the epithelia

Function: allows materials to pass by diffusion and filtration in the sites where protection is not important; secretes lubricating substances in serosae.

Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae)

Simple Cuboidal Epithelium

Description: single layer of cube-like cells with large, spherical central nuclei

Function: secretion and absorption

Location: kidney tubules; ducts and secretory portions of small glands; ovary surface

Simple Columnar Epithelium

Description: single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)

Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cell) by ciliary action.

Location: non ciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.

Pseudostratified Columnar Epithelium

Description: single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting goblet cells and bear cilia.

Function: secretes substances, particularly mucus; propulsion of mucus by ciliary action

Location: non ciliated type in male's sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.

Stratified Squamous Epithelium

Description: thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cels are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.

Function: protects underlying tissues in areas subjected to abrasion

Location: non keratinized type forms the moist lining of the esophagus mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.

Transitional Epithelium

Description: resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamous-like, depending on degree of organ stretch

Function: stretches readily and permits distension of urinary organ by contained urine

Location: lines the ureters, urinary bladder, and part of the urethra.

Skeletal Muscle

Description: long, cylindrical, multinucleate cells; obvious striations

Function: voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control

Location: in skeletal muscles attached to bones or occasionally skin

Cardiac Muscle

Description: branching, striated, generally uninucleate cells that interdigitate at specialized junctions called intercalated discs

Function: as it contracts, cardiac muscle propels blood into the circulation; involuntary control

Location: the walls of the heart

Smooth Muscle

Description: spindle-shaped cells with central nuclei; no striations; cells arranged closely to form sheets

Function: propels substances (foodstuffs, urine) or a baby along internal passageways; involuntary control

Location: mostly in the walls of hollow organs

Nervous Tissue

Description: neurons are branching cels; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are non excitable supporting cells

Function: neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neuron

Location: brain, spinal cord, and nerves

Connective Tissue Proper: Loose Connective Tissue Areolar

Description: Gel-like matrix with all three fiber types: fibroblasts, macrophages, mast cells, and some white blood cells

Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid

Location: Widely distributed under epithelia of body, e.g. forms lamina propria of mucous membranes; packages organs; surrounds capillaries.

Connective Tissue Proper: Loose Connective Tissue Adipose

Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet

Function: Provides reserve fuel; insulates against heat loss; supports and protects organs

Location: under skin; around kidneys and eyeballs; within abdomen; in breasts

Connective Tissue Proper: Loose Connective Tissue Reticular

Description : Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network

Function: Fibers form a soft internal skeleton (stroma) that supports other cell types, including white blood cells, mast cells, and macrophages

Location: lymphoid organs (lymph node, bone marrow, and spleen)

Connective Tissue Proper: Dense Regular

Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast

Function: Attaches muscles to bones or to other muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction

Location: Tendons, most ligaments, aponeuroses

Connective Tissue Proper: Elastic

Description: Dense regular connective tissue containing a high proportion of elastic fibers

Function: allows recoil of tissue following stretching; maintains pulsating flow of blood through arteries; aids passive recoil of lungs following inspiration

Location: walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes.

Connective Tissue Proper: Dense Irregular

Description: primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast

Function: able to withstand tension exerted in many directions; provides structural strength

Location: fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract

Cartilage: Hyaline

Description: amorphous but firm matrix; collagen fibers forms an imperceptible network; chondroblasts produce the matrix and, when mature (chondrocytes), lie in lacunae

Function: supports and reinforces; serves as resilient cushion; resists compressive stress

Location: forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx

Cartilage: Elastic

Description: similar to hyaline cartilage, but more elastic fibers in matrix

Function: maintains the shape of a structure while allowing great flexibility

Location: supports the external ear (auricle); epiglottis

Cartilage: Fibrocartilage (Fibrous)

Description: Matrix similar to but less firm than matrix in hyaline cartilage; thick collagen fibers predominate

Function: tensile strength with the ability to absorb compressive shock

Location: intervertebral disc; pubic symphysis; disc of knee joint

Bones (Osseous Tissue)

Description: hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized

Function: bones support and protects (by enclosing); provides lavers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis)

Location: bones

Blood

Description: red and white blood cells in a fluid matrix (plasma)

Function: transport of respiratory gases, nutrients, wastes, and other substances

Location: contained within blood vessels