TISSUES

Tissues

• Cells are organized into sheets or groups called tissues.

• There are four major tissue types found in the body: – epithelial tissue (ET)– connective tissue (CT)– muscle tissue– nervous tissue

Epithelial Tissue (ET)• Epithelia are sheets of cells that function in

protection, secretion, absorption, and excretion.

• Epithelium is composed of tightly packed cells anchored to a basement membrane.

• It lacks blood vessels and rapidly divides.

• ET are classified by cell shape and number of cell layers.

Structure Location Function

• thin, single cell

• diffusion, cushion

• air sacs, blood vessels

Structure Location Function

• boxy, single cell

• absorption, secretion

• kidneys, ducts of glands

Structure Location Function

• tall, single cell

• protection, secretion, absorption

• digestive tract

Structure Location Function

• tall, un-uniform single layers

• protection, secretion

• trachea

• fallopian tubes

Structure Location Function

• flat, multi-layered

• protection, keep out anything “unwanted”

• keratinized – epidermis

•non-keratinized – mouth, anus

Structure Location Function

• shape changing, single layer

• shape changing, stretching

• urinary bladder

Connective Tissues (CT)

• Connective tissue is the most abundant tissue in the body.

• Extracellular material, a matrix, makes up the bulk of the tissue.

• Matrix is composed of fibers and ground substance.

• Connective tissue cells usually can divide.

NAME DESCRIPTION LOCATION FUNCTION

MESENCHYME precursor matrix Embryo gives rise to all other CT’s

AREOLAR gel-like matrix with fibroblasts, collagen and elastic fibers

beneath ET (serous membranes around organs & lining cavities)

cushions, diffusion, inflammation

ADIPOSE closely packed adipocytes with nuclei pushed to side

beneath skin, breasts, around kidneys & eyeballs

insulation, energy store, protection

RETICULAR reticular net of fibers in loose matrix; lymphocytes and reticulocytes

basement membrane,lymph organs

support

DENSEREGULAR

dense matrix of collagen fibers

tendons, ligaments attachment (high tensile strength)

DENSEIRREGULAR

loose matrix of collagen fibers

dermis of skin tensile strength

ELASTIC CT matrix of elastic fibers lung tissue, wall of aorta durability with stretch

HYALINECARTILAGE

chondrocytes in lacunae in amorphous matrix

embryo skeleton, costal cartilage, tip of nose, trachea, larynx

support

FIBRO-CARTILAGE

less firm than above intervertebral discs, pubic symphysis

tensile strength, shock absorber

ELASTICCARTILAGE

above plus elastic fibers external ear, epiglottis shape maintenance plus flexibility

BONE concentric circles of calcified matrix

bones support, protection, movement, Ca ++ store, hematopoiesis

BLOOD red and white cells; platelets in plasma

in heart, and blood vessels transport of nutrients, wastes & gases

CT Cell Types

• Three types of CT cells…

– Fibroblasts

– Macrophages

– Mast Cells

Loose Connective Tissue• Loose CT or areolar tissue binds organs together and

holds tissue fluids.

• It forms thin membranes found beneath the skin, between muscles, and beneath epithelial tissue.

Reticular Connective Tissue• Reticular connective tissue supports organs.

Dense Connective Tissue• Dense connective tissue binds organs together.

• It is found in tendons, ligaments, and the dermis of the skin. *CONTAINS COLLAGEN

Elastic Connective Tissue• Elastic connective tissue supports, protects, and

provides a flexible framework.

• It connects vertebrae and is found in the walls of arteries and airways.

Adipose Tissue• Adipose tissue protects, insulates, and stores fat in

droplets inside the cells.

• It is found beneath the skin, around the kidneys, behind the eyes, and on the heart.

Cartilage (CT)

• Cartilage is a rigid connective tissue.

• Cartilage lacks blood vessels.

• Thee types of Cartilage…

– Hyaline cartliage– Elastic cartliage– Fibrocartliage

Bone• Bone supports, protects, provides a framework for

muscle attachment.

Blood• Blood transports gases, nutrients, and wastes,

defends against disease, and acts in clotting.

Muscle Tissue (MT)

There are three types of muscle tissue: skeletal, smooth, and cardiac.

Properties:• It is contractile (muscle fibers can shorten and

thicken).• It is excitable.

Structure Location Function

• found in bundles, contracts

• movement• on the skeleton – whole body

Structure Location Function

• thin, smooth, tapered

• peristalsis• digestive tract

Structure Location Function

• thick, with striated bands

• keep heart beating – does not tire easy

• heart

Nervous Tissues• Nervous tissue is excitable like muscle tissue.• It is found in the brain, spinal cord, and peripheral

neurons.• Nerve cells or neurons sense changes and transmit

signals.