Body Tissues and Membranes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lecture Outline

Body Tissues oComposed of specialized cells of similar structure and perform a common function oFour major types (4 C’s mneumonic) Epithelial - Cover Connective - Connect Muscular - Contract Nervous - Communicate oOrgans are typically composed of all 4 types of tissue

Epithelial Tissue oCells are tightly packed oProtects external and internal body surfaces oAlso secretes and absorbs substances oEpithelial cells can divide to replace lost or damaged cells oCells are avascular (lack a blood supply) oHas a free surface and a basement membrane

Epithelial Tissue oClassification of epithelial tissue Number of cell layers  Simple epithelial tissue is one cell layer thick  Stratified epithelial tissue is composed of two or more layers Shape of the cells  Squamous epithelium has flattened cells  Cuboidal epithelium has cube-shaped cells  Columnar epithelium has elongated cells Two additional special tissues

Epithelial Tissue Squamous Epithelium  Simple squamous epithelium  Composed of a single layer of flattened cells  Found in areas where simple diffusion occurs

Epithelial Tissue  Stratified squamous epithelium  Has many cell layers  Shape of deeper cells may be cuboidal or columnar  Shape of outer cells are flattened and squamous-shaped  Found in the outer portion of the skin and in body orifices

Epithelial Tissue Cuboidal Epithelium  Simple cuboidal epithelium  Single layer of cube-shaped cells attached to a basement membrane  Found in glands where its function is secretion  Covers the ovaries  Lines most of the kidney tubules where it absorbs and secretes substances  Stratified cuboidal epithelium  Often only has two layers  Mostly found lining the larger ducts of certain glands

Epithelial Tissue Columnar Epithelium  Simple columnar epithelium  Cells are longer than they are wide  Modified to perform particular functions  Lines digestive organs and the uterine tubes  Stratified columnar epithelium  Not very common  Located in parts of the pharynx and in the male urethra

Epithelial Tissue Pseudostratified Columnar Epithelium  Appears to have more than one layer of cells, but only has one true layer  Each cell touches the basement membrane  Pseudostratified ciliated columnar epithelium lines parts of the reproductive system and air passageways of the respiratory system

Epithelial Tissue Transitional Epithelium  Changes in response to tension  Located in urinary bladder, the ureters, and part of the urethra  Allows these organs to stretch

Connective Tissue oBinds structures together, provides support and protection, produces blood cells, and stores fat oCells are separated by an extracellular matrix that is composed of an organic ground substance that contains the following fibers: Collagen fibers Elastic fibers Reticular fibers

Connective Tissue oFibrous Connective Tissue Loose (areolar) connective tissue  Cells of this tissue are mainly fibroblasts  Contains many collagen and elastin fibers in a fine web like arrangement  Adipose tissue is a type of loose connective tissue in which the cells enlarge and store fat

Connective Tissue Dense connective tissue  Has thick bundles of collagen fibers  In dense regular connective tissue the bundles are parallel (as in tendons and ligaments)  In dense irregular connective tissue the bundles run in different directions (in the dermis)  In reticular connective tissue the cells are called reticular cells and the matrix contains only reticular fibers (also called lymphatic tissue)

Connective Tissue oCartilage Cells called chondrocytes are found in small chambers called lacunae Because it is avascular, it heals slowly Hyaline cartilage  Most common type  Contains only collagen fibers  Found in the nose, ends of long bones and ribs, and in the supporting rings of the trachea Elastic cartilage  Matrix contains many elastic fibers; also contains collagen fibers; more flexible than hyaline cartilage  Found in the outer ear Fibrocartilage  Matrix contains strong collagen fibers  Absorbs shock and reduces friction between joints  Found between the vertebrae and in the knee joint

Connective Tissue oBone Extremely hard matrix composed of mineral salts deposited around collagen fibers Osteocytes (bone cells) Compact bone Spongy bone

Connective Tissue oBlood Composed of formed elements (cells)  Red blood cells (erythrocytes) - carry oxygen  White blood cells (leukocytes) – fight infection  Platelets (thrombocytes) – blood clotting Matrix is called plasma and is not formed by the tissue cells

Muscular Tissue oSkeletal Muscle (voluntary muscle) Attached to bones of the skeleton Causes movement of body parts Have a cylindrical shape and are long Muscle fibers (cells) have multiple, peripherally located nuclei Muscle fibers appear striated due to the placement of actin and myosin filaments in the fiber

Muscular Tissue oSmooth Muscle (visceral muscle) Spindle-shaped cells Not under voluntary control (involuntary) Found in the walls of hollow viscera (organs)

Muscular Tissue oCardiac Muscle Found only in the walls of the heart Pumps blood Cardiac muscle cells have striations, like skeletal muscle Is involuntary, like smooth muscle Cardiac muscle cells have a single, centrally located nucleus Cardiac muscle cells are bound to one another by intercalated disks

Nervous Tissue oFound in the brain and spinal cord oNeurons (nervous tissue cells) generate and conduct nerve signals. oA neuron has three parts: Dendrite – receives an impulse Cell body – contains the nucleus Axon – conducts nerve impulses oNeuroglia (more numerous nervous tissue cells)

Nervous Tissue oNeuroglia (more numerous nervous tissue cells) oSupport and nourish neurons oTypes of neuroglia found in the brain: Microglia Astrocytes Oligodendrocytes Ependymal cells oSchwann cells are neuroglia located outside the brain or spinal cord

Extracellular Junctions oJunctions between cells help cells function as a tissue oTypes of cell junctions: Tight junction – plasma membrane proteins join, forming an impermeable barrier Gap junction – plasma membrane channels join, allowing substances to pass between the two cells Adhesion junction (desmosome) – adjacent plasma membranes held together by extracellular filaments

Glands oConsists of one or more cells that produce and secrete a product oMost are composed primarily of epithelium oExocrine glands – secrete their product onto the outer surface or into a cavity oEndocrine glands are ductless and secrete their product internally to be transported by the bloodstream

Membranes oMucous membranes Line interior walls of the organs and tubes that open to the outside of the body Consist of epithelium overlying a layer of loose connective tissue Epithelium contains goblet cells that secrete mucus

Membranes oSerous membranes Parietal membranes line the thoracic and abdominopelvic cavities Visceral membranes cover internal organs Consist of a layer of simple squamous epithelium overlying a layer of loose connective tissue Secrete serous fluid that lubricates the membranes Pleura – serous membranes in the thorax  Parietal pleura – lines thoracic wall  Visceral pleura – covers the surface of the lungs Pericardium – covers the heart Peritoneum – serous membranes within the abdomen  Parietal peritoneum – lines the abdominopelvic wall  Visceral peritoneum – covers the organs in the abdominopelvic cavity

Membranes oSynovial membranes Line freely movable joint cavities Composed of connective tissue Secrete synovial fluid that lubricates the ends of bones oMeninges Found within the posterior cavity Composed entirely of connective tissue Protective covering for the brain and spinal cord

Membranes oCutaneous membrane (skin) Forms the outer covering of the body Consists of an outer portion of keratinized stratified squamous epithelium attached to a thick layer of dense connective tissue