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Transcript
Introduction to Tissues, Organ Systems, and Homeostasis Chapter 4 Homeostasis • Stable operating conditions in the internal environment • Brought about by coordinated activities of cells, tissues, organs, and organ systems Tissue • A group of cells and intercellular substances that interact in one or more tasks • Four types Epithelial tissue Muscle tissue Connective tissue Nervous tissue Organs • Group of tissues organized to perform a task or tasks • Heart is an organ that pumps blood through body • Heart consists of muscle tissue, nervous tissue, connective tissue, and epithelial tissue Organ Systems • Organs interact physically, chemically, or both to perform a common task • Circulatory system includes the heart, the arteries, and other vessels that transport blood through the body Epithelial Tissue • Lines the body’s surface, cavities, ducts, and tubes • One free surface faces a body fluid or the environment basement membrane simple squamous epithelium connective tissue Simple Epithelium • Consists of a single layer of cells • Lines body ducts, cavities, and tubes • Cell shapes: Squamous Cuboidal Columnar Stratified Epithelium • Two or more layers thick • Functions in protection, as in skin • Cells in the layers may be squamous, columnar, or cuboidal Glands • Secretory organs derived from epithelium • Exocrine glands have ducts or tubes • Endocrine glands are ductless Cell Junctions • Tight junctions prevent leaks • Gap junctions connect abutting cytoplasms • Adhering junctions cement cells together Connective Tissue • Most abundant tissue in the body • Cells are scattered in an extracellular matrix • Matrix is collagen and/or elastin fibers in a polysaccharide ground substance Soft Connective Tissues Loose connective tissue Dense, irregular connective tissue Dense, regular connective tissue Specialized Connective Tissues Cartilage Bone Adipose tissue Blood • Classified as a connective tissue because blood cells arise in bone • Serves as the body’s transport medium • Red cells, white cells, and platelets are dispersed in a fluid medium called plasma Muscle Tissue • Composed of cells that contract when stimulated • Helps move the body and specific body parts Three Types of Muscle • Skeletal muscle • Smooth muscle • Cardiac muscle Skeletal Muscle • Located in muscles that attach to bones • Long, cylindrical cells are striated • Cells are bundled closely together in parallel arrays Smooth Muscle • In walls of many internal organs and some blood vessels • Cells are not striped and taper at the ends Cardiac Muscle • Present only in the heart • Cells are striated and branching • Ends of cells are joined by communication junctions Nervous Tissue • Detects stimuli, integrates information, and relays commands for response • Consists of excitable neurons and supporting neuroglial cells Neurons • Excitable cells • When stimulated, an electrical impulse travels along the plasma membrane • Arrival of the impulse at the neuron endings triggers events that stimulate or inhibit adjacent neurons or other cells Neuroglia • Constitute more than half of the nervous tissue • Protect and support the neurons, both structurally and metabolically Replacement Tissues • Artificial skin • Bioengineered cartilage and bone • Organoapatites and coral to repair bone Stem Cells • Have the potential to develop into different kinds of mature cells • Embryonic cells most useful but use of embryos as source is controversial • Some adult tissues also may provide stem cells Membranes • Epithelial tissue membranes – Mucous membranes – Serous membranes – Cutaneous membrane • Connective tissue membranes – Synovial membranes Major Organ Systems • Integumentary • Lymphatic • Muscular • Respiratory • Skeletal • Urinary • Nervous • Circulatory • Endocrine • Reproductive Major Body Cavities • Cranial cavity • Spinal cavity • Thoracic cavity • Abdominal cavity • Pelvic cavity Planes of Symmetry Frontal plane (aqua) Transverse plane (yellow) Midsagittal plane (green) Primary Tissues • In vertebrate embryos, cells become arranged to form three primary tissues Ectoderm Mesoderm Endoderm • These give rise to all adult tissues Functions of Human Skin • Protects the body from injury, dehydration, UV radiation, and some pathogens • Helps control temperature • Receives some external stimuli • Produces vitamin D Structure of Human Skin • Part of body’s integument • Two layers – Outer epidermis – Inner dermis • Atop a layer of hypodermis Epidermis • Stratified epithelium • Grows from bottom upward • Most abundant cells are keratinproducing keratinocytes • Melanocytes produce the brown pigment melanin Dermis • Dense connective tissue with many elastin and collagen fibers • Includes blood vessels, lymph vessels, and receptor endings of sensory nerves Sweat Glands • Arise from epidermal cells • Composition of sweat – 99% water, with dissolved salts, trace of ammonia (waste product) • Controlled by sympathetic nerves Oil Glands • Also called sebaceous glands • Derived from epidermal cells • Secretions lubricate and soften hair and skin; also kill many surface bacteria • Acne occurs when bacteria infect oilgland ducts Hair • Root is embedded in skin • Cells near the base of root divide, push cells above them upward • Hair follicles nourished by the dermis • Shaft of dead cells extends above the skin surface UV Damages Skin • UV light stimulates melanin production in skin; produces a tan • Tan is the body’s way of protecting itself against UV • Prolonged sun exposure causes elastin fibers to clump, skin to age prematurely, increases risk of cancer Body Fluids • The human body contains about 15 liters of fluid • Fluid outside of cells is extracellular fluid – Interstitial fluid lies between cells – Plasma is the fluid portion of the blood Fluid Balance • Changes in extracellular fluid cause changes in cells • The component parts of every animal work to maintain a stable fluid environment for living cells Homeostasis • Stable operating conditions in the internal environment STIMULUS (input into the system) RECEPTOR (e.g., free nerve ending in the skin) INTEGRATOR (such as the brain) EFFECTOR (a muscle or a gland) Response to the stimulus leads to change. Change is “fed back” to the receptor. RESPONSE (system’s output) Negative Feedback • Some activity alters a condition in the internal environment • Alteration triggers a response • Response reverses the altered condition Positive Feedback • Some activity alters the internal environment • The alteration triggers a response • The response intensifies the change in the internal condition