Transcript Histology
Histology Human Anatomy and Physiology What Is a Tissue? Tissue = cells organized into layer or groups Cells separated by nonliving, intercellular materials Solid minerals in bone Liquid plasma in blood How Are Tissues Maintained? Stem cells = cells that have the ability to divide many times and yield new cells that then specialize Groups of stem cells set aside in tissues to replace worn or damaged parts 4 Major Types of Tissues Tissues Epithelial Connective Simple Squamous Simple Cuboidal Areolar (Loose) Adipose Simple Columnar Pseudostratified Columnar Reticular Dense Stratified Squamous Stratified Cuboidal Elastic Cartilage Stratified Columnar Transitional Hyaline Elastic Glandular Fibrocartilage Exocrine Glands Endocrine Glands Bone Muscle Skeletal Cardiac Blood Nervous Smooth Embryonic Germ Layers General Characteristics of Epithelial Tissue Widespread throughout the body Basement membrane Lacks blood vessels Divides readily Tightly packed Classified according to shape and number of layers Simple Squamous Epithelium Simple Squamous continued… Functions: Allows substances to pass easily Forms walls of capillaries Lines air sacs (alveoli) of lungs Lines insides of blood and lymph vessels Covers membranes that line body cavities Simple Cuboidal Epithelium Simple Cuboidal continued… Functions: Covers the ovaries Lines the kidney tubules Lines ducts of the salivary glands, pancreas, and liver Secretion and absorption Simple Columnar Epithelium May be ciliated or nonciliated Goblet cells Microvilli Functions: Absorption Movement of substances Secretion Nonciliated Simple Columnar Epithelium Ciliated Simple Columnar Epithelium Pseudostratified Columnar Epithelium Pseudostratified Columnar continued… Functions: Lines the passages of the respiratory system Lines ducts of glands and sperm-carrying ducts Stratified Squamous Epithelium Stratified Squamous continued… Functions: Keratinized form makes up the epidermis Nonkeratinized lines the oral cavity, throat, vagina, and anal canal Stratified Cuboidal Epithelium Functions: Lines larger ducts of mammary glands, sweat glands, salivary glands, and pancreas Forms lining of developing ovarian follicles and seminiferous tubules Stratified Columnar Epithelium Functions: Lines vas deferens and some parts of the pharynx Protection Secretion Transitional Epithelium Transitional Epithelium continued… Functions: Forms the inner lining of the urinary bladder Lines the ureters and part of the urethra Expandable lining Blocks urine from diffusing back into the body Glandular Epithelium Specialized to produce and secrete substances into ducts or into body fluids Glands classified as endocrine or exocrine Types of Glands Endocrine secretes products into tissue fluids or blood Exocrine secretes products into ducts that open onto an internal or external surface Merocrine release fluid products by exocytosis Holocrine release entire cells that later disintegrate Apocrine lose small portions of glandular cells Endocrine Glands Pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas Will be discussed in more detail later Exocrine Glands Goblet cells Intestinal glands, sweat glands, mucous glands in small intestine, sebaceous glands, bulbourethral glands of male, salivary glands Classification of Connective Tissue Mesenchyme General Characteristics of Connective Tissue Most abundant type of tissue by weight Large amounts of matrix between cells Matrix contains fibers and ground substance Vascularity Major cell types: Fiber types: Fibroblast Macrophage Mast Cell Collagenous Elastic Reticular Connective tissue proper and specialized connective tissues Areolar Connective Tissue Also known as loose connective tissue Mainly fibroblasts Collagenous and elastic fibers Areolar Connective Tissue continued… More Areolar Connective Tissue Functions: Binds the skin to underlying organs Fills spaces between muscles Lies beneath most epithelium layers Blood vessels nourish epithelial cells Adipose Tissue Also known as fat Adipocytes store fat in their cytoplasm Amount in the body reflects diet or endocrine disorder Adipose Tissue continued… Functions: Lies beneath skin, in spaces between muscles, around the kidneys, behind the eyeballs, in some abdominal membranes, on the surface of the heart, in breasts, and around some joints Cushions joints and some organs Insulation Stores energy Reticular Connective Tissue Reticular fibers Numerous fibroblasts and white blood cells Reticular Tissue continued… Function: Provides supportive framework in walls of certain internal organs, such as the liver, spleen, and lymphatic organs Regular Dense Connective Tissue Closely packed collagenous fibers, fine network of elastic fibers Few cells, mostly fibroblasts Regular dense connective tissue – very organized fibers Regular Dense continued… Functions: Attaches muscles to bones or to other muscles Attaches bones to bones Withstands great tensile stress when pulling force is applied in one direction Makes up tendons and most ligaments Irregular Dense Connective Tissue Thicker, interwoven, and more randomly organized fibers Irregular Dense continued… Functions: Able to withstand tension exerted in many directions Provides structural strength Makes up dermis of skin, submucosa of digestive tract, fibrous capsules Elastic Connective Tissue Elastic fibers in parallel strands or branching networks Collagenous fibers and fibroblasts between elastic fibers Found in ligamenta flava and within walls of some large arteries, some portions of the heart, and larger airways Cartilage Rigid connective tissue Functions: Provides support, frameworks, and attachments Protects underlying tissues Forms structural models for developing bones Many collagenous fibers Chondrocytes and lacunae Perichondrium Lacks direct blood supply Types distinguished by types of intercellular material Hyaline Cartilage Most common type of cartilage Collagenous fibers form imperceptible network Chondroblasts form matrix and mature into chondrocytes Hyaline Cartilage continued… Functions: Supports and reinforces Has resilient cushioning properties Resists compression stress Found on ends of bones in joints, soft part of nose, trachea, larynx, and costal cartilages of ribs Forms most of embryonic skeleton Important in bone growth and repair of fractures Elastic Cartilage More flexible than hyaline cartilage Elastic fibers in matrix Elastic Cartilage continued… Functions: Maintains the shape of a structure while allowing greater flexibility Provides the framework for the external ears and parts of the larynx Fibrocartilage Very tough cartilage Many large collagenous fibers Fibrocartilage continued… Functions: Tensile strength Shock absorber Forms intervertebral disks, disks in knee joint, and pubic symphysis Compact Bone Also called osseous tissue Most rigid connective tissue Mineral salts in matrix Large amounts of collagen Osteocytes Bone continued… Functions: Supports and protects by enclosing Provides levers for muscles to act on Stores calcium and other minerals Marrow inside bones is site of hematopoiesis Blood Blood plasma Red blood cells, white blood cells, and platelets Most blood cells formed in red bone marrow Functions: transport gases, fight infection, clotting Will be discussed in more detail later General Characteristics of Muscle Tissues Contractile Elongated cells Three types classified according to striations and nuclei Will be discussed more later Types of Muscle Skeletal Smooth Cardiac Skeletal Muscle Long and narrow cells Striations Multinucleate cells Skeletal Muscle continued… Functions: Voluntary movement Locomotion Manipulation of the environment Facial expression Voluntary control Attached to bones and occasionally skin Smooth Muscle No striations Spindle-shaped cells Single, centrally located nucleus Smooth Muscle continued… Functions: Propels substances or objects along internal passageways Involuntary Found mostly in walls of hollow organs Cardiac Muscle Striated cells joined end to end Cells form complex, branching network Intercalated disks Usually uninucleate Cardiac Muscle continued… Functions: Involuntary Propels blood into the circulation Found only in the heart General Characteristics of Nervous Tissue Neurons Neuroglia Will be discussed more later Nervous Tissue continued… Functions: Transmits electrical signals from sensory receptors and to effectors (muscles and glands) Found in brain, spinal cord, and nerves