Sensor that monitors the environment and responds to changes (i.e., stimuli) by sending information to the control center. Control center Determines

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1 Introduction Overview Terms o Anatomy = studies the structure of body parts and their relationships to one another o Physiology = studies the functions of the body and how the body parts work and carry out their lifesustaining activities Levels of Structural Organization The levels of structural organization of the body, from simplest to most complex, are: o Chemical o Cellular o Tissue o Organ o Organ system o Organism The eleven organ systems of the body are: o Integumentary o Skeletal o Muscular o Nervous o Endocrine o Cardiovascular o Lymphatic & Immune o Respiratory o Digestive o Urinary o Reproductive Maintaining Life Necessary Life Functions o All living organisms carry out certain vital functional activities necessary for life, including: Maintenance of boundaries Movement Responsiveness Digestion Metabolism Excretion Reproduction Growth Survival Needs o Nutrients o Water o Oxygen o Appropriate temperature o Appropriate atmospheric pressure Homeostasis A dynamic equilibrium (i.e., balance) of the internal environment. All body systems contribute to homeostasis, but the nervous and endocrine systems are most important Homeostasis is necessary for health Homeostatic Control o All homeostatic control mechanisms are processes involving at least three components working together Receptor

2 Sensor that monitors the environment and responds to changes (i.e., stimuli) by sending information to the control center. Control center Determines the set point (i.e., the level or range at which a variable is to be maintained) Analyzes the input it receives Determines the appropriate response or course of action Effector Provides the means for the control center s response to the stimulus Results of the response then feedback to influence the effect of the stimulus, either by: o Reducing it so that the whole control process is shut off (negative feedback) Most homeostatic control mechanisms are negative feedback mechanisms. All negative feedback mechanisms have the same goal: Prevent sudden severe changes within the body For example, heart rate, blood pressure, rate/depth of breathing, blood volume, body temperature, and blood levels of oxygen, carbon dioxide and minerals. o Enhancing it so that the whole process continues at an even faster rate (positive feedback) This feedback mechanism is positive because the change that results proceeds in the same direction as the initial change, causing the variable to deviate further from its original value or range Positive feedback mechanisms usually control infrequent events that do not require continuous adjustments They are likely to race out of control so are rarely used to promote the moment-to-moment well-being of the body. Examples include: the enhancement of labor contractions during birth and blood clotting. Homeostatic Imbalance o Most disease can be regarded as a result of homeostatic disturbance o Natural aging process Our body s control systems become less efficient as we age Our internal environment becomes less stable with time o Feedback mechanism imbalance At times the usual negative feedback mechanism is overwhelmed and positive feedback mechanisms take over. For example, heart failure.

3 Tissues of the Body Overview Tissues = groups of cells that are similar in structure and perform a common or related function Four primary tissue types make up the body o Epithelial (covering) o Connective (support) o Muscle (movement) o Nervous (control) Epithelial Tissue A sheet of cells that covers a body surface or lines a body cavity It occurs in the body as: o Covering and lining epithelium Forms the outer layer of skin, inner and outer lining of most organs, and body cavities o Glandular epithelium Creates the glands of the body; glands consist of one or more cells that make and secrete (export) a particular product (i.e., secretion) Nearly all substances received or given off by the body must pass through an epithelium All epithelial sheets rest upon and are supported by connective tissue. o For example, although epithelium is innervated (supplied by nerve fibers), it is avascular (contains no blood vessels); epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue. Functions o Protection o Absorption o Filtration o Excretion o Secretion o Sensory reception Connective Tissue Connective tissue is found everywhere in the body The most abundant and widely distributed of the primary tissues Main classes of Connective Tissue o Connective Tissue Proper (including fat and fibrous tissue of ligaments) o Cartilage o Bone Tissue o Blood Functions o Binding and support o Protection o Insulation o Transportation of substances within the body (regarding blood) Structural Elements of Connective Tissue o Ground Substance o Fibers Unstructured material that fills the space between the cells and contains the fibers It holds large amounts of fluid and functions as a medium through which nutrients and other dissolved substances can diffuse between the blood capillaries and the cells The fibers of connective tissue provide support Three types of fibers found in connective tissue Collagen fibers o These fibers are extremely tough and provide high tensile strength to the connective tissue

4 o Cells o When fresh they have a glistening white appearance (aka, white fibers) Elastic fibers o These fibers contain a rubber-like protein that allows them to stretch and recoil like rubber bands. o Fresh elastic fibers appear yellow (aka, yellow fibers) Reticular fibers o Short, fine, collagenous fibers that are continuous with collagen fibers and they branch extensively, forming delicate networks that surround small blood vessels and support the soft tissue of organs. Each major class of connective tissue has a fundamental or resident cell type that exists in immature and mature forms All of these cells have a suffix -blast meaning forming or literally bud or sprout They secrete the ground substance and the fibers characteristic of their particular matrix The primary blast cell types are: Fibroblasts (connective tissue) Chondroblasts (cartilage) Osteoblasts (bone) Other cell types include: Fat cells (adipose cells) store nutrients White blood cells migrate into the connective tissue matrix from bloodstream to defend against and fight infections Mast cells act as sentinels to detect foreign microorganisms (e.g., bacteria, fungi) and initiate local inflammatory responses against them Macrophages large, irregular shaped cells that avidly eat or phagocytize a broad variety of foreign material. Types of Connective Tissue o Connective Tissue Proper Loose connective tissue Areolar connective tissue Adispose (fat) tissue Reticular connective tissue Dense connective tissue Dense regular connective tissue Dense irregular connective tissue Elastic connective tissue Cartilage Hyaline cartilage Elastic cartilage Fibrocartilage Bone Blood Nervous Tissue Main component of the nervous system the brain, spinal cord, and nerves which regulates and controls body functions To be discussed during the nervous system section of the course. Muscle Tissue Highly cellular, well-vascularized tissues that are responsible for most types of body movement. Consist of three kinds of muscle tissue: o Skeletal o Cardiac o Smooth

5 To be discussed during the muscular system section of the course. Covering and Lining Membranes Cutaneous Membrane o Refers to our skin o It is an organ system consisting of a keratinized epithelium (epidermis) firmly attached to a thick layer of dense irregular connective tissue (dermis). Mucous Membranes o Line body cavities that open to the exterior o They are wet or moist, membranes bathed by secretions or, in the case of urinary mucosa, urine. Serous Membranes o Moist membranes found in the closed body cavities. o Cells within this membrane ad a thin, clear serous fluid that lubricates the membranes and the surrounding organs. These are all continuous multicellular sheets composed of at least two primary tissue types o Epithelium bound to an underlying layer of connective tissue proper Steps of Tissue Repair Inflammation sets the stage o Tissue trauma causes injured tissue cells (e.g., macrophages and mast cells) to release inflammatory chemicals which cause capillaries to dilate and become very permeable. o White blood cells and plasma fluid enter the area bringing clotting proteins, antibodies and other substances o Clot forms which stops blood loss and creates a scab. Organization restores the blood supply o Organization = the first phase of tissue repair; blood clot is replaced by granulation tissue (i.e., new capillaries and fibroblasts) o New capillaries are laid down o New collagen fibers are created and bridge the gap o Macrophages digest the original blood clot and collagen fiber deposit continues o Scar tissue is formed Regeneration and fibrosis effect permanent repair o Surface epithelium begins to regenerate under the scab during organization phase o The regenerated epithelium thickens until it finally resembles that of the adjacent skin