Human Anatomy & Physiology

Human Anatomy & Physiology Chapter 5: Tissues Panda Wilson

II. A. What are tissues? and C. What is the matrix? A tissue is a group of similar cells specialized to carry out a specific function • In addition to cells, all tissues include a non-living portion called the extracellular matrix (composition of the matrix varies from tissue to tissue). The function of the extracellular matrix is: • to support the cells within the tissue and • to transmit signals from outside the cells into cells (these signals influence how cells function Panda Wilson

II. B. The major tissue types & their functions • Epithelial – cover & protection of organs, to participate in secretion, absorption, excretion of various substances, and sensory reception • Connective – bind body parts together, support & protect softer body parts, and produce blood cells • Muscle – produce movement by contraction & relaxation • Nervous – sensory reception and transmitting impulses for coordination, regulation, & integration of body functions Panda Wilson

III. Epithelial Tissues • Epithelial tissues cover body surfaces & organs; lines inner surface of body cavities and inner surface of hollow organs; compose glands. • Characteristics are: • Lack blood vessels so nutrients must diffuse into epithelium from underlying connective tissues; anchored to underlying connective tissue by a thin, non-living layer called the basement membrane (which is part of the extracellular matrix) Panda Wilson

III. Epithelial Tissues • Classified according to types of cells • Squamous: thin, flattened cells • Cuboidal: cube-shaped cells • Columnar: tall, elongated cells • and number of cell layers: • Simple: single layer • Stratified: two or more layers • Pseudostratified: a single layer of cells that appears to be layered because the cell nuclei are a varying levels along a row of aligned cells Panda Wilson

Squamous Epithelium Simple Squamous Stratified Squamous Panda Wilson

Cuboidal Epithelium Simple Cuboidal Stratified Cuboidal Panda Wilson

Columnar Epithelium Simple Columnar Stratified Columnar Panda Wilson

Pseudostratified vs Stratified Pseduostratified Stratified Panda Wilson

III. C. Simple Squamous Epithelium 2. Because substances easily pass through simple squamous epithelium, it is found where diffusion and filtration take place. For example: • alveoli in lungs where gas exchange takes place • walls of capillaries, linings of blood & lymph vessels • covers membranes that line body cavities Because it is so thin & delicate, simple squamous tissue is easily damaged. Panda Wilson

III. D. Simple Cuboidal Epithelium • Simple cuboidal tissue covers the ovaries, lines most of the kidney tubules and the ducts of certain glands (ex: salivary, thyroid, pancreas, & liver) • The functions of simple cuboidal tissue are secretion and absorption and, in glands, secretion of glandular products. Panda Wilson

III. E. Simple Columnar Epithelium • Simple columnar tissue is a single layer of elongated (more long than wide) cells that may, or may not, be ciliated (the cilia are in constant motion so they function to move objects along the surface if the tissue). • Ciliated simple columnar tissue lines the fallopian tubes from the ovaries to the uterus; non-ciliated simple columnar tissue is found in the digestive tract. • Ciliated cells aid in movement of substances; in the digestive tract, non-ciliated cells protects underlying tissues, absorbs nutrients, and secretes various fluids. Panda Wilson

III. F. Pseudostratified Columnar Epithelium Cilia are a characteristic of pseudostratified columnar epithelial which lines the passages of the respiratory tract. • The respiratory tract linings are mucous-covered & sticky in order to trap dust and microorganisms entering with air. The cilia move the mucous & its captured particles upward and out of the respiratory airways. Panda Wilson

III. G . Stratified Squamous Epithelium • Cell division takes place in the deeper layers that are closer to the basal membrane & the nutrient supply of the underlying connective tissue. the layers are pushed upward and outward as new cells are produced. As the cells move outward they become more flattened. • S. S. E. forms the outer layer of the skin, & is found in the lining of the oral cavity, throat, vagina, and anal canal. Panda Wilson

III.H. Transitional Epithelium • Transitional epithelium is specialized to change in response to increased tension (in other words, it “stretches”). • T. E. forms the inner lining of the urinary bladder (where it also forms a barrier to prevent contents of the urinary system from diffusing back into the internal environment). • T. E. also lines the ureters (from kidney to bladder) and part of the urethra (bladder to outside). Panda Wilson

III.I. Glandular Epithelium • Glandular epithelium is composed of cells that are specialized to produce & secrete substances into ducts or into body fluid. (Usually cuboidal or columnar epithelia.) Note: exocrine vs endocrine glands • Exocrine glands secrete their products into ducts that open onto surfaces (such as the skin or the lining of the digestive tract). • Endocrine glands secrete their products into tissue fluid or blood. Panda Wilson

III.J. Types of Glandular Secretions • Merocrine • a water, protein-rich fluid product is released through the cell membrane by exocytosis • ex: salivary glands, sweat glands, pancreatic glands • merocrine glands release secretions without losing any of the cell’s cytoplasm Panda Wilson

III.J. Types of Glandular Secretions • Apocrine • The secretions apocrine glands consist of cellular product & portions of the free end of glandular cells is released through the cell membrane by exocytosis • ex: mammary glands, ceruminous glands lining the external ear canal • apocrine glands lose small portions of their bodies during secretion Panda Wilson

III.J. Types of Glandular Secretions • Holocrine • entire cells filled with secretory products disintegrate • ex: sebaceous glands of the skin Panda Wilson

IV. Connective Tissues: Structure &Characteristics • cells are farther apart than epithelial cells & have an abundance of extracellular matrix (consistence varies from fluid to semisolid to solid) • can usually divide • varying degrees of vascularity (blood vessels) but usually have good blood supplies and are well nourished • Types: bone (most rigid), cartilage (less rigid than bone), dense connective tissue (more flexible; ex: tendons & ligaments), adipose tissue, loose connective tissue (aka areolar tissue), blood (fluid) Panda Wilson

IV. A. Connective Tissues: Functions • bind structures • provide support & protection • serve as frameworks • store fat • produce blood cells • protect against infections • help repair tissue damage Panda Wilson

IV. Connective Tissues: Components of Connective Tissue Cell Type Tissue Fiber Collagenous –tensile strength Elastic – stretches Reticular – very thing collagenous fibers that provide net-like, delicate support networks • Fibroblast – produce fibers • Macrophages – carry on phagocytosis • Mast cells – secrete heparin & histamine Panda Wilson

IV. B. Connective Tissues: Cell Type Functions • Fibroblast • most common “fixed” cells (fixed = not mobile) • produce fibers by secreting protein into the matrix • Macrophages • aka histiocytes; begin as white blood cells • act as scavengers & defensive cells against foreign particles; they are phagocytes (“eat” cell!! – engulf & break down foreign particles) • Mast cells • very large cells found near blood vessels • release heparin (prevents blood clotting) & histamine (promotes reactions associated with inflammation & allergies) Panda Wilson

IV. C. Collagenous vs Elastic • Collagenous Fibers • Very strong which allows the tissues to withstand pulling forces • Little ability to stretch • Elastic Fibers • Great ability to stretch • Not as strong as collagenous fibers Note: blood supply to dense connective tissue (make up tendons & ligaments) is poor = SLOW to heal Panda Wilson

IV. D. Ligament vs Tendon Note: blood supply to dense connective tissue (make up tendons & ligaments) is poor = SLOW to heal • BOTH are collagenous fibers • Ligaments connect bones to bones • Tendons connect muscles to bones Panda Wilson

IV. E. Adipose Tissue • Specialized form of loose connective tissue that develops when fat droplets are stored in the cytoplasm of adipocytes • Lies beneath the skin between muscles, around the kidneys, behind the eyeballs, in certain abdominal areas, on the surface of the heart, and around certain joints. • Adipose tissue cushions joints & some organs (ex: kidneys); it also provides insulation and energy storage (in fat molecules) Panda Wilson

IV. F. Types of Cartilage General Characteristics • A rigid connective tissue that provides support, frameworks, and points of attachment ; also forms structural models for many developing bones • Has no direct blood supply; nutrients diffuse into cartilage from surrounding perichondrium • This is reason that torn cartilage heals slowly and why chondrocytes do not divide frequently Panda Wilson

IV. F. Types of Cartilage • Hyaline cartilage • Most common; very fine fibers (looks ~ like white glass) • Found on the ends of bones in many joints, soft part of the nose, & in the supporting rings of the respiratory passages • Function to cushion shock in joints and as a model for development & growth of some types of bone) Panda Wilson

IV. F. Types of Cartilage • Elastic cartilage • More flexible than hyaline due to having a network of elastic fibers • Provides the flexible framework for external ear (pinna) and the larynx • Fibrocartilage • Very tough • Acts as a shock absorber for structures subject to pressure; for ex: forms pads (intevertabral disc )between vertebrae and cushions bones in the knee and pelvic girdle Panda Wilson

IV. G. Bone • Bone is the most rigid of the connective tissues: • Hardness due to the deposition of mineral salts between the cells • Functions are: • supports body structure • protect vital body parts • provide points of attachment for muscles (making movement possible) • Contains red marrow which forms blood cells and maintains calcium & phosphorus balance • Bone injuries heal relatively quick Panda Wilson

IV. G. Bone • Bone injuries heal relatively quick because of good blood supply. (The central canal of bones contains a blood vessel.) Panda Wilson

IV. H. Blood (Vascular Connective Tissue) 1. Blood is composed of formed elements (cells) suspended in a fluid extracellular matrix called blood plasma. 2. The formed elements (cells) are • red blood cells (RBCs) • white blood cells (WBCs) • platelets (cell fragments) Panda Wilson

IV. H. 3. Connective Tissue Matrix The connective tissue matrix is the key to connecting cells to tissues: • it is composed of the basement membrane and the interstitial matrix (the material between cells) • serves as a scaffolding to organize cells into tissues • it relays biochemical signals that control cell division, differentiation, movement, & migration. Panda Wilson

V. Muscle • The characteristic of muscle tissue is its ability to contract (shorten) in response to stimuli. As they contract, the muscle fibers pull at their attached ends and thus move body parts. Panda Wilson

V. Muscle Skeletal muscle • long, thread-like cells that have alternating light & dark striations • controlled by conscious effort (hence the alternative description of “voluntary muscle”) • Skeletal muscle is found in muscles that attach to bone allowing body movement Panda Wilson

V. Muscle Smooth muscle • no striations, shorter than skeletal muscle cells and are more spindle-shaped • not controlled by conscious effort – its actions are involuntary • comprises the walls of hollow organs such as the stomach, intestine, urinary bladder, uterus, and blood vessels • Moves food through the digestive tract, constricts blood vessels, and empties the urinary bladder Panda Wilson

V. Muscle Cardiac muscle • Striated and branched; are joined end-to-end forming complex networks • not controlled by conscious effort – its actions are involuntary • comprises the bulk of the heart • pumps blood through the heart chambers and into blood vessels Panda Wilson

VI. Nervous Tissue • The basic cell of nervous tissue is the neuron. • Neuroglial cells support and bind cells, carry on phagocytosis, & help supply nutrients to nerve cells by connecting them to blood vessels. • Nervous tissue senses changes in the internal & external environment, interprets those changes, and responds by sending impulses to effectors (such as muscles, glands, or organs) Panda Wilson

VII. Membranes Membranes are considered organs because they are comprised of at least two kinds of tissues. There are 3 major types of membranes: • Serous membranes • Mucous membranes • Cutaneous membranes A fourth type of membrane, synovial membrane, lines joints such as the knee. Panda Wilson

VII. Membranes • Serous membrane • Lines body cavities that lack opening to the outside; form the lining of the thorax (parietal pleura), and abdomen (parietal peritoneum), and the organs within these cavities (visceral pleura & peritoneum) • Mucous membrane • line cavities that open to the outside of the body; ex: oral & nasal cavities and the tubes of the digestive, respiratory, urinary, & reproductive systems • mucous membranes contain goblet cells that secret mucus Panda Wilson

VII. Membranes • Cutaneous membrane is more commonly referred to as the skin. Panda Wilson

Human Anatomy & Physiology