AnP Q1_5 Body Tissues.pptx

BODY TISSUES TISSUES Groups of cells that are similar in structure and function. The study of tissues is histology The four primary tissue types – epithelium, connective tissue, nervous tissue and muscle – interweave to form the ‘fabric’ of the body  If we had to assign a single term...

BODY TISSUES TISSUES Groups of cells that are similar in structure and function. The study of tissues is histology The four primary tissue types – epithelium, connective tissue, nervous tissue and muscle – interweave to form the ‘fabric’ of the body  If we had to assign a single term to each primary tissue type that would best describe its overall role it would most likely be: Covering (epithelium) Support (connective) Movement (muscle) Control (nervous) However, these terms reflect only a tiny fraction of the functions that each of these tissues perform. EPITHELIAL TISSUE EPITHELIAL TISSUE Aka: Epithelium The lining, covering and glandular tissue of the body Covering and lining epithelium covers all free body surfaces and contains versatile cells Glandular epithelium forms various glands Functions include: protection, absorption, filtration and secretion Epithelium of the skin protects against bacterial and chemical damage Epithelial linings of the stomach and small intestine absorb food into the body In the kidneys, epithelium both absorbs and filters Secretion is a specialty of the glands, which produce such substances as perspiration, oil, digestive enzymes and mucus Special Characteristics of the Epithelial Tissue Fit closely together to form continuous sheets The membranes always have one free (unattached) surface or edge This so-called apical surface is exposed to the body’s exterior or to the cavity of an internal organ The lower surface rests on a basement surface, a structureless material secreted by the cells Have no blood supply of their own (avascular) and depend on diffusion for food and oxygen If well nourished, can regenerate easily Classification of Epithelium Each epithelium is given two names The first indicates the relative number of cell layers: (1) simple epithelium (one layer of cells) (2) stratified epithelium (more than one cell layer) The second describe the shape of the cells: (1) squamous (flattened like fish scales) (2) cuboidal (shaped like dice) (3) columnar (shaped like columns) The stratified epithelia are named for the cells at the free surface of the epithelial membrane  Simple Epithelium Most concerned with absorption, secretion and filtration Because simple epithelia are usually very thin, protection is NOT one of their specialties Simple Squamous Epithelium Single layer of thin squamous cells resting on a basement membrane Cells fit together much like floor tiles Usually forms where filtration or exchange of substances by rapid diffusion occurs Is in the air sacs of the lungs Also forms the serous membranes or serosae (the slick membranes that line the ventral body cavity and cover the organs in that cavity Simple Squamous Epithelium Simple Cuboidal Epithelium Single layer of cuboidal cells resting on a basement membrane Common in glands and their ducts (e.g. salivary glands and pancreas) Forms the walls of the kidney tubules Covers the surface of the ovaries Simple Cuboidal Epithelium Simple Columnar Epithelium Single layer of tall cells that fit closely together Goblet cells, which produce a lubricating mucus, are often seen in this type of epithelium Goblet cells are intestinal mucosal epithelial cells that serve as the primary site for nutrient digestion and mucosal absorption Simple Columnar Epithelium Lines the entire length of the digestive tract from the stomach to the anus Epithelial membranes that line body cavities open to the body exterior are called mucosae or mucous membranes Simple Columnar Epithelium Pseudostratified Columnar Epithelium All of its cells rest on a basement membrane. However, some cells are shorter than others and their nuclei appear at different heights above the BM. Mainly functions in absorption and secretion A ciliated variety called pseudostratified ciliated columnar epithelium lines most of the respiratory tract Pseudostratified Columnar Epithelium  Stratified Epithelium Consist of two or more cell layers Epithelium of the skin and many mucous membranes (e.g. mouth, esophagus, rectum, conjunctiva and vagina Being considerably more durable than the simple epithelia, these variety functions primarily to protect Stratified Squamous Epithelium Most common stratified epithelium in the body Consists of several layers of cells Found in sites that receive a good deal of abuse or friction – e.g. the esophagus, the mouth and the outer portion of the skin Stratified Squamous Epithelium  Stratified Epithelium Stratified Cuboidal Epithelium Usually has just two cell layers Fairly rare in the body being found mainly in the ducts of large glands – mammary glands, sweat glands, salivary glands and pancreas Also found in ovarian follicles and seminiferous tubules Stratified Cuboidal Epithelium  Stratified Epithelium Stratified Columnar Epithelium Columnar cells with basal cells varying in size and shape Found in male urethra, vas deferens and parts of the pharynx Stratified Columnar Epithelium  Stratified Epithelium Transitional Epithelium (Urothelium) Highly modified stratified squamous epithelium that forms the lining of only a few organs – the urinary bladder, the ureters and part of the urethra Subject to considerable stretching Transitional Epithelium  Glandular Epithelium A gland consists of one or more cells that make and secrete a particular product This product is called a secretion Two major types: (1) endocrine and (2) exocrine  Glandular Epithelium Endocrine glands Lose their connections to the surface (duct), thus they are often called ductless glands Secretions (all hormones) diffuse directly into the blood vessels Examples: thyroid, adrenals, pituitary  Glandular Epithelium Exocrine glands Retain their ducts Secretions empty through the ducts to the epithelial surface Examples: sweat and oil glands, liver, pancreas Glandular Epithelium CONNECTIVE TISSUE  CONNECTIVE TISSUE As the name suggests, connects body parts Found everywhere in the body The most abundant and widely distributed of the tissue type Primarily involved in protecting, supporting and binding together other body tissues  FUNCTIONS Support Structural & Mechanical Packing Fills spaces, Shape to the organ Storage Adipose tissue: energy Loose areolar CT: water & electrolytes Transport Medium for nutrients & metabolic wastes Repair Fibroblasts: matrix and fibers Defense Cells: Phagocytosis or Antibodies Common Characteristics of the Connective Tissue 1) Variations in blood 2) Extracellular supply matrix Most connective tissues Made up different are vascularized (have types of cells plus a good blood supply) varying amounts of a Tendons and nonliving substance ligaments are found outside the cells avascular called the (consequently heal very extracellular matrix slowly when injured)  Types of Connective Tissues From most rigid to softest, the major connective tissue classes are: 1. Bone 2. Cartilage 3. Dense connective tissue 4. Loose connective tissue Major differences reflect fiber type and the number of fibers in the matrix  Bone Sometimes called osseous tissue Composed of bone cells sitting in cavities called lacunae and surrounded by layers of a very hard matrix that contains calcium salts in addition to large numbers of collagen fibers Its rocklike hardness is crucial in its ability to protect and support other body organs  Cartilage Less hard and more flexible than bone Most widespread is the hyaline cartilage which forms the supporting structure of the larynx, attaches the ribs to the breastbone, and covers the ends of bones where they form joints The highly compressible fibrocartilage forms the cushion-like disks between the vertebrae of the spinal column Elastic cartilage is found where a structure is desired – e.g. the external ear  Dense Connective Tissue Aka: Dense fibrous tissue Has collagen fibers as its main matrix element Forms strong, rope-like structures such as tendons and ligaments Tendons attach skeletal muscle to bones Ligaments connect bones to bones at joints  Loose Connective Tissue Relatively speaking, are softer and have more cells and fewer fibers than any other connective tissue type except blood Includes: Areolar Adipose Reticular Blood  Loose Connective Tissue Areolar Tissue Most widely distributed connective tissue variety in the body A soft, pliable, cobwebby tissue that cushions and protects the body organs it wraps. When a body region is inflamed, the areolar tissue in the area soaks up the excess fluid like a sponge, and the area swells and becomes puffy, a condition called edema.  Loose Connective Tissue Adipose Tissue Commonly called fat Forms the subcutaneous tissue beneath the skin, where it insulates the body and protects it from extremes of both heat and cold Protects some organs individually – e.g. kidneys and eyeballs There are also fat “depots” in the body, such as the hips and breasts, whre fat is stored and available for fuel if needed  Loose Connective Tissue Reticular Tissue Consists of a delicate network of interwoven reticular fibers Forms the stroma or internal supporting framework which can support many free blood cells in lymphoid organs such as lymph nodes, the spleen and bone marrow  Loose Connective Tissue Blood Aka: Vascular tissue Considered a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma Transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases and many other substances throughout the body MUSCLE TISSUE  MUSCLE TISSUE Highly specialized to contract or shorten to produce movement Because muscle cells are elongated to provide a long axis for contraction, they are called muscle fibers  Muscle Tissue Skeletal Muscles Attached to the skeleton Can be controlled voluntarily Form the flesh of the body, the so-called muscular system The result of their action is gross body movement or changes in our facial expression Cells are long, cylindrical, multinucleate and have obvious striations  Muscle Tissue Smooth Muscles Aka: Visceral muscles Why smooth? No striations are visible Cells have a single nucleus and are spindle-shaped (pointed at each end) Found in the walls of hollow organs such as the stomach, bladder, uterus and blood vessels  Muscle Tissue Cardiac Muscles Found only in the heart Has striations Cells are uninucleate, branching that fit together at junctions called intercalated disks Under involuntary control NERVOUS TISSUE  NERVOUS TISSUE All neurons receive and conduct electrochemical impulses from one part of the body to another Two major functional characteristics: 1. irritability 2. conductivity  NERVOUS TISSUE The structure of neuron is unique The cytoplasm is drawn out into long extensions (as much as 3 feet or more in the leg), which allows a single neuron to conduct an impulse over long distances in the body Neurons along with supporting cells make up the nervous system BACK TO YOU