Tissue Types Tissue refers to a group of cells that work together in the body. The cells of a tissue share: An embryonic origin. Morphological features. Arranged in an orderly pattern to perform their function. Four broad categories of tissues: epithelial, connective, muscle, and nervous. The cell types are characterized by specific functions that contribute to the overall health and maintenance of the body. A disruption of the structure of a tissue is a sign of injury or disease. Histology - the microscopic study of tissue appearance, organization, and function.

Embryonic origin The zygote, or fertilized egg, is a single cell formed by the fusion of an egg and sperm. After fertilization the zygote goes through many rapid mitotic cycles, forming an embryo. The first embryonic cells are totipotent meaning they have the ability to differentiate into any type of cell in the body. There are three major cell lineages established within the embryo. Each forms the distinct germ layers from which all the tissues and organs of the human body eventually form. Three germ layers identified by their relative position:  ectoderm (ecto- = “outer”) mesoderm (meso- = “middle”) endoderm (endo- = “inner”). 

Four Types of Tissue Epithelial tissue (epithelium) - sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Connective tissue - binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body.  Muscle tissue - excitable, responding to stimulation and contracting to provide movement. Three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart.  Nervous tissue - excitable, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body.

Epithelial tissue simple = single layer stratified = multiple layers *Naming is based on description* simple = single layer stratified = multiple layers   squamous = flat cuboidal = square columnar = column (rectangle) The cells are arranged in different forms, each form has a different function.

Simple Squamous Form: Flat and thin Tissue Form: Flat and thin Function: diffusion and filtration. Air sacs in lungs, capillaries

Stratified Squamous Multi layer squamous, functions in protection Found lining body cavities; skin and mouth

Simple Cuboidal Function: Secretion and absorption Found in kidneys tubules, ducts and covering the ovaries

Simple Columnar Function: Secretion and absorption Found in digestive tract and uterus *Contains scattered goblet cells to secrete mucus *Can have microvilli

Pseudostratified Columnar Appear stratified, but just a single layer of cells, nuclei at different levels Can have cilia (hair-like projections) And goblet cells, which secrete mucus Function: Secretion and cilia-aided movement Location: lining air passages and tubes of the reproductive system

Transitional Epithelium Stretchable Blocks diffusion (no leaking) Found in the urinary bladder

Glandular Epithelium Cells are specialized to secrete substances They make up the GLANDS                      exocrine glands         endocrine glands    Examples:    salivary, sweat            hormones

Loose Connective Tissue Binds underlying organs to skin and to each other Forms delicate thin membranes throughout the body

Adipose Tissue (fat) Energy Storage

Fibrous Connective Tissue Tendons =  muscles to bones   Ligaments = bones to bones

Hyaline Cartilage Location: covers ends of joints, nose and respiratory passages, serves as padding

Elastic cartilage Location: External Ear and Larynx

Fibrocartilage Tough, shock absorbing Location: Between vertebrae

Bone Tissue (Osseus)

Blood Tissue

Cardiac muscle

Skeletal muscle (striated)

Smooth muscle

Nerve Tissue

organs Several types of tissues come together to form a working unit, an organ. Knowledge of tissues will help you understand how organs function.