HISTOLOGY Intercellular organization

Types of Tissues The cells of the body are arranged into various groups having similar structural and functional characteristics. These groups are called tissues. Epithelium Connective tissue Muscle tissue Nervous tissue

Epithelial Tissue Tissues that cover and line all surfaces and cavities of the body. These cells are close together with very little intercellular material. Can be arranged in one layer (simple) or more than one layer (stratified) Functions include: protection, absorption, and secretion Some possess specialized structures, such as cilia and microvilli.

3 cell shapes of epithelium Squamous (looks like a fried egg) Cuboidal cube shaped Columnar column shaped

Epithelium (cont.) There are no blood capillaries present in epithelium So all nutrients and oxygen reach these cells by diffusion They also have the ability to replace themselves at a very high rate.

Epithelium (cont.)

Connective Tissue Consists of various types of cells, fibers, and proteins known as intercellular material. (matrix) Functions include: support, flexibility, and binding of tissues, transport and storage of materials and protection against foreign substances. There are many diverse forms. It can be a liquid, gel, fibrous, or solid. Connective tissue has the capacity to repair and regenerate damaged areas of the body.

MUSCLE TISSUE Displays contractility, the ability to shorten when stimulated. It accounts for 40-50% of the total body weight. Functions in the production of movement. 3 types of Muscle: Skeletal-produces movement of the bones of the skeleton acting as levers Smooth-produces movement within the hollow organs of the body and the blood vessels. Cardiac- found only in the heart, causes the contraction of the heart to pump blood.

NERVOUS TISSUE Is specially adapted to collect and transmit information by means of different types of nerve cells. Nerve cells are called NEURONS Nerve cells differ a great deal in structure and function Some are sensitive to changes in the environment and can receive stimuli. Others are adapted for sending impulses or messages down their length. Other nerve cells are responsible for carrying out the proper responses. Nervous tissue plays a vital role in the maintenance of homeostasis.

Types of Epithelial Tissue Simple Squamous Epithelium – squamous cell is a flattened (fried egg) shaped cell. Found lining the blood vessels. endothelium Makes up the tissues of the lungs, the sac around the heart. Functions in absorption/diffusion, and the secretion of fluids.

Stratified Squamous Epithelium Makes up the skin, lines all body orifices. Many layers of squamous cells. The skin is cornified (keratin) a protein which makes the cells tougher and impervious to water in its more superficial layers. Functions in protection and secretion.

Simple Cuboidal Epithelium One layer of cube shaped cells. Found making up glands, tubules of the kidneys, and the ovaries. Functions in secretion.

Simple Columnar Epithelium One layer of column shaped cells. They are packed close together to form a protective covering over the inner surface of a hollow organ. The lining of the digestive tract is composed of these types of cells. Found within this epithelium are goblet cells which secrete mucous which allows for lubrication and protection of these cells. Functions in protection, secretion and absorption.

Ciliated Columnar Epithelium (Pseudostratified) Appear to be stratified but are not. Free border of the cell is covered with cilia, which moves material. (mucous) Found lining most of the respiratory tract and the fallopian tubes. Functions in protection and secretion.

CONNECTIVE TISSUES 3 cell types found in connective tissue. 1.fibroblast-long star shaped cell produces elastin(yellow) and collagen (white) fibers. 2.Macrophages-phagocytic cell. 3.Mast Cells- function in immunity still not clearly understood.

Loose Connective Tissue (areolar) Forms delicate thin membranes with many yellow and white fibers. Binds skin to underlying tissue and organs Has numerous blood vessels running through it to supply the epidermis with nourishment. Fills in spaces, repairs damaged tissues.

Adipose Tissue Fat storage tissue Found deep to the skin, around kidneys, heart, behind eyeballs and in abdominal membranes, and in various joints. Acts as a protective cushion, heat insulator, and a reserve energy source.

Fibrous Connective Tissue Consists of closely packed thick white fibers. (collagen) very few cells. Makes up ligaments, tendons, outer membrane of the eye (sclera), and deeper portions of the dermis. Very low blood supply so healing is very slow.

Cartilage Very rigid, supports, provides framework, serves as attachments for muscles, and protects. Very abundant intercellular matrix with collagen fibers imbedded in it. Cells are called chondrocytes, which produce a clear milk-glass like matrix. No direct blood supply so healing is slow. 3 types found in the body. 1.hyaline-most abundant found on the ends of bones in joints, nose, rings of trachea and the fetal skeleton. 2.Elastic- more flexible found in the external ear, and larynx 3.Fibrocartilage-very tough shock absorber. Found in the intervertebral discs, knees, and bones of the pelvic girdle.

Bone (Osseous Tissue) Most rigid of all tissues. Contains mineral salts of calcium and phosphorus. Very large intercellular matrix like cartilage. Functions to provide support, serves as attachment for muscles, forms blood cells, protects internal organs, and stores inorganic salts. Cell are called osteocytes

Blood The only true liquid tissue of the body Actually is cells suspended in a liquid intercellular matrix. (plasma) Blood cells are produced in hemopoietic tissue called red marrow in the bones of the skeleton.

MUSCLE TISSUE Displays irritability, ability to respond to a stimulus. contractile Contracts or shortens when stimulated 3 types: 1.skeletal-striated, multinucleated, very large cells. Responsible for voluntary movements of the skeleton. voluntary- you consciously control its contractions. 2.Smooth-nonstriated, involuntary found in the walls of hollow organs and blood vessels. Pushes food through the alimentary canal and controls the flow of blood thru the vessels. 3.Cardiac-striated, involuntary muscle makes up the heart, singlely nucleated, possess intercalated discs.

NERVOUS TISSUE Also displays irritability, made up of neurons, which are sensitive to certain changes in the environment. They respond by transmitting electrical impulses down cytoplasmic extensions to other neurons or muscles or organs. Makes up the brain and spinal cord and the rest of the peripheral nerves and receptors. Neuroglial cells function to bend, support and supply nutrients to neurons.