Chapter 5: Tissues
Describe the general characteristics and functions of epithelial tissues.
- Epithelial tissue is widespread throughout the body; it covers organs and lines body cavities and hollow organs - Epithelial tissues are anchored to a basement membrane, are made up of tightly packed cells containing little intercellular material, generally lack blood vessels, and readily divide - Epithelial tissues function in protection, secretion, absorption, and excretion - Classification is by cell shape (squamous, cuboidal, columnar) and the number of layers ( simple - 1 layer or stratified more than 1 layer)
List the four major tissue types, and indicate a function of each type.
1. Epithelial tissue - forms protective coverings and functions in secretion and absorption 2. Connective tissue - supports and binds structures together 3. Muscular tissue - body movement 4. Nervous tissue - conducts impulses to control and coordinate body activities
Name the types of epithelium and identify an organ in which is found.
1. Simple squamous epithelium - made up of a single layer of thin, flattened cells. Suited for diffusion; functions in the exchange of gases in the alveoli of the lungs and lines blood and lymph vessels as well as body cavities. 2. Simple cuboidal epithelium - single layer of cube-shaped cells with centrally located nuclei. Functions in secretion and absorption in the kidneys, secretion in glands, and covers the ovaries. 3. Simple columnar epithelium - made up of one row of elongated cells whose nuclei are all located near the basement membrane. Nonciliated lines the uterus, stomach, and intestines where it protects underlying tissues, secretes digestive fluids, and absorbs nutrients. Ciliated is found in the uterine tubes and moves an egg toward the uterus. In the intestine, these cells possess microvilli that increase the surface area available for absorption. 4. Pseudostratified columnar epithelium - These cells appear layered due to the varying positions of their nuclei within the row of cells, but are not truly layered. Cilia may be present, along with mucus- secreting globlet cells, that line and sweep debris from respiratory tubes. 5. Stratified squamous epithelium - This type of tissue is made up of layers of flattened cells that are designed to protect underlying layers. It makes up the outer layer of skin, and lines the mouth, throat, vagina, and anal canal. In the skin, outer layers of cells undergo keratinization, producing a dry, water-proof, protective layer; however, this process does not occur where tissues remain moist in the throat, vagina, or anal canal. 6. Stratified cuboidal epithelium - This tissue consists of two to three layers of cuboidal cells lining a lumen of the mammary glands, sweat glands, salivary glands, pancreas, ovarian follicles, and seminiferous tubules. Several layers of cells provide greater protection than one single layer. 7. Stratified columnar epithelium - This tissue consists of several layers of cells with columnar cells on the surface. This type of tissue is rare, but may sometimes be found in the male urethra. 8. Transitional epithelium - designed to distend and return to its normal size, as it does in the lining of the urinary bladder, urethra, and ureters. This design provides distensibility and keeps urine from diffusing back into the internal cavity. 9. Glandular epithelium - This tissue is made up of cuboidal or columnar cells designed to produce and secrete substances into ducts or into body fluids.
Explain how glands are classified.
Glands are classified by the ways the glands secrete their products. a. Merocrine glands release fluid products by exocytosis. Includes the pancreas, salivary glands, sweat glands, and most other glands. Lower body temperature. b. Apocrine glands pinch off a portion of their cell bodies during secretion; mammary glands. wet skin during pain, fear, emotional upset, and sexual arousal. c. Holocrine glands release entire cells that disintegrate to release their secretions; sebaceous (oil) glands
Describe the general characteristics and functions of nervous tissues.
Nervous tissues are found in the brain, spinal cord, and nerves. - Neurons, or nerve cells conduct electrical impulses to other neurons, muscles, and glands. - Neurons have unique cellular extensions. Helper cells, or neuroglia, support, nourish, and communicate with the neurons but do not conduct impulses.
Distinguish among the four major types of membranes.
A. Epithelial membranes are thin, sheet-like structures composed of epithelium and connective tissues, covering body surfaces and lining body cavities. 1. Serous membranes - double membranes that line body cavities that are not open to the outside (thorax and abdominal cavities) 2. Mucous membranes line cavities and tubes that are open to the outside 3. Cutaneous membrane - the skin; a dry membrane that is keratinized for protection and water-proofing. 4. Synovial membrane - found in joints, made of cells that produce and secrete synovial fluid; provide lubrication for less friction when joints move.
Describe the major functions of each type of connective tissue.
Connective tissues bind, support, protect, serve as frameworks, fill spaces, store fat, produce blood cells, protect against infection, and help repair tissue damage. Loose connective tissue: Areolar tissue - binds organs (beneath skin in subcutaneous layer, between muscles, beneath epithelial tissues) Adipose tissue - protects, insulates, stores fat (beneath skin, around kidneys, behind eyeballs, on surface of heart) Reticular connective tissue - supports walls of internal organs (walls of liver and spleen) Dense connective tissue: Hyaline cartilage - supports, protects, provides framework (ends of bones, nose, rings in the walls of respiratory passages) Elastic cartilage - supports, protects, provides flexible framework (framework of external ear and parts of larynx) Fibrocartilage - supports, protects, absorbs shock (between bony parts of spinal column, parts of pelvic girdle and knee) Bone - supports, protects, provides framework (bones of skeleton) Blood - transports substances , helps maintain stable internal environment (throughout body within a close system of blood vessels and heart chambers)
Distinguish among the three types of muscle tissues.
1. Skeletal muscle is attached to bone and can be controlled by conscious effort (voluntary). The cells (muscle fibers) are long and cylindrical, striated, have many nuclei and contract from nervous impulse. 2. Smooth muscle tissue lacks striations, is uninucleated, and consists of spindle-shaped cells. 3. Cardiac muscle tissue is found only in the heart and consists of branching fibers that are connected to each other with intercalated discs.
