Bisc 102 Notes - Chapter 23: Animal Tissues and Organ Systems
Bisc 102 Notes - Chapter 23: Animal Tissues and Organ Systems Bisc 102
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This 4 page Class Notes was uploaded by Alexis Neely on Friday October 7, 2016. The Class Notes belongs to Bisc 102 at University of Mississippi taught by Carla Beth Carr in Fall 2016. Since its upload, it has received 4 views. For similar materials see Inquiry Into Life Human Biology in College of Liberal Arts at University of Mississippi.
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Date Created: 10/07/16
23.1 Specialized Cells Build Animal Bodies - Anatomy, the study of an organism’s structure, describes the parts that compose the body - that is, its form. Physiology is a related discipline that considers how those parts work - their function. - Biologists describe the animal body in terms of an organizational hierarchy. Most animals have tissues, which are groups of specialized cells that interact and provide a specific function. The inner lining of the stomach, for example, is a tissue that secretes stomach acid. An organ consists of two or more interacting tissues that function as a unit. The stomach is an organ that consists of muscle, blood and nerves in addition to the tissue of its inner lining. Still farther up the organizational hierarchy are o rgan systems, which consist of two or more organs that are physically or functionally joined. 23.2 Animals Consist of Four Tissue Types - Together, these interacting cells form tissues that fall into four broad categories: epithelial, connective, muscle, and nervous. - All animal tissues have a feature in common: The cells are embedded in a nonliving extracellular matrix, which is a mixture of water, carbohydrates, lipids, and (usually) protein fibers such as collagen and elastin. Interestingly, most normal body cells cannot survive or replicate when removed from the extracellular matrix. Somehow, cancer cells escape this “anchorage dependence,” breaking away from the extracellular matrix yet retaining the ability to divide. These abnormal cells also often secrete enzymes that destroy the fibers of the extracellular matrix, clearing the way for cells from a cancerous tumor to invade adjacent tissues. Epithelial Tissue Covers Surfaces - Epithelial tissues coat the body’s internal and external surfaces with one or more layers of tightly packed cells. They cover organs and line the inside of hollow organs and body cavities. The diverse functions of epithelial tissues include protection, nutrient absorption along the intestinal tract, and gas diffusion in the lungs. These tissues also form glands, organs that secrete substances into ducts or into the bloodstream (e.g. breast milk, sweat, saliva, etc.) - Epithelial tissues always have a “free” surface that is exposed either to the outside or to a space within the body. On the opposite side, epithelium is anchored to underlying tissues by a layer of extracellular matrix called the basement membrane. The epithelial cells are often connected to one another, forming leak-proof sheets. The tightly knit structure of epithelial tissue is closely tied to its function as a border between the body’s tissues and an open space. - About 90% of human cancers arise in epithelial tissues. Such a cancer is called a carcinoma. The most common carcinomas include cancers of the skin, breast, lung, prostate and colon. Most Connective Tissues Bind Other Tissues Together - The most widespread tissue type in a vertebrate’s body is c onnective tissue, which consists of cells that are embedded within the extracellular matrix rather than being attached to one another. Connective tissues fill spaces, attach epithelium to other tissues, protect and cushion organs, and provide both flexible and firm structural support. Unlike epithelial tissues, connective tissues never coat any body surface. - Connective tissues are extremely variable in both structure and function. Loose connective tissue binds other tissues together and fills the space between organs; dense connective tissue builds ligaments and tendons; and adipose tissue stores energy as fat. Blood is a connective tissue, as are the cartilage and bone that make up the vertebrate skeleton. A close look at figure 23.3 reveals that in all connective tissues except adipose tissue, the extracellular matrix occupies more volume than do the cells. - Blood is an unusual tissue because it is a liquid, not a solid. It consists of red blood cells, white blood cells, and cell fragments called platelets, all traveling in a liquid called plasma. The extracellular matrix of blood is unique in two ways: It is a fluid and it lacks protein fibers. Muscle Tissue Provides Movement - Muscle tissue consists of cells that contract (become shorter) when electrically stimulated. Contraction occurs when long, thin protein filaments inside the muscle cells slide past one another. Abundant mitochondria in muscle cells provide the energy for contraction, and the heat generated by muscle contraction is important in body temperature regulation. - The most familiar function of muscle tissue, however, is to move other tissues and organs. Muscle cells attach to soft tissue or bone; when the cells contract, the body part moves. Digestion, the elimination of wastes, blood circulation, and the motion of the limbs all rely on muscle contraction. - Animal bodies contain three types of muscle tissue. Skeletal muscle tissue consists of long cells. When viewed with a microscope, this tissue appears striped or striated because the protein filaments that fill each cell align in a repeated pattern. Most skeletal muscle attaches to bond and provides voluntary movements that a person can consciously control. Nervous Tissue Forms a Rapid Communication Network - Nervous tissue uses electrical signals to convey information rapidly within an animal’s body. Sensor cells detect stimuli such as the scent of a rose or a prick of its thorn. Other cells then transmit that information along nerves to the central nervous system (brain and spinal cord), which helps you interpret what you experience. - Two main cell types occur in nervous tissue: neurons and neuroglia. Neurons form communication networks that receive, process, and transmit information. The cell may connect to another neuron at a junction called a synapse, or it may stimulate a muscle or gland. Neuroglia are cells that support neurons and assist in their functioning. 23.3 Organ Systems are Interconnected The Nervous and Endocrine Systems Coordinate Communication - The human nervous system, which consists of the brain, spinal cord, and nerves, specializes in rapid communication. - The endocrine system includes glands that secrete hormones, which are communication molecules that affect development, reproduction, mental health, metabolism, and many other functions. Hormones travel within the circulatory system and stimulate a characteristic response in target organs. Hormones act relatively slowly, but their effects last longer than nerve impulses. The Skeletal and Muscular Systems Support and Move the Body - The skeletal system consists of bonds, ligaments, and cartilage. Bones protect underlying soft tissues and serve as attachment points for muscles. The marrow within some bones produces the components of blood; bones also store minerals such as calcium. - Individual skeletal muscles are the organs that make up the muscular system. The Digestive, Circulatory, and Respiratory Systems Work Together to Acquire Energy - The organs of the digestive system dismantle food, absorb the small molecules, and eliminate indigestible wastes. - The circulatory system transports these food molecules (and many other substances) throughout the body. Nutrients absorbed by the digestive system enter blood at the intestines. The heart pumps the nutrient-laden blood through blood vessels that extend to all of the body’s cells. - The respiratory system exchanges gases with the atmosphere. Cellular respiration requires not only food but also oxygen gas (O ), which diffuses into blood at the lungs. 2 The circulatory system delivers the O thro2 out the body. Blood also carries carbon dioxide gas (CO ),2 waste product of cellular respiration, to the lungs to be exhaled. The Urinary, Integumentary, Immune, and Lymphatic Systems Protect the Body - Cell metabolism generates many waste products in addition to CO . These was2s enter the blood, which circulates through the kidneys. These organs are part of the u rinary system, the organs that remove water-soluble nitrogenous wastes and other toxins from blood and eliminate them in urine. The kidneys also have other protective functions; they adjust the concentrations of many ions, balance the blood’s pH, and regulate blood pressure. - One line of physical protection is the i ntegumentary system, which consists of skin, associated glands, hair, and nails. Skin is a waterproof barrier that helps keep the underlying tissues moist, blocks the entry of microorganisms, and helps maintain body temperature. - The body also fights infection and cancer. The i mmune system is a huge army of specialized cells, organs, and transport vessels. This complex system attacks cancer cells, viruses, microbes, and other foreign substances. Moreover, the immune system has a “memory” of previous infections. - The lymphatic system is a bridge between the immune system and the circulatory system. Lymph originates as fluid that leaks out of blood capillaries and fills the spaces around the body’s cells. Lymph capillaries absorb the excess fluid and pass it through the lymph nodes, where immune system cells destroy foreign substances. The fluid then returns to the circulatory system. The Reproductive System Produces the Next Generation - The reproductive system consists of organs that produce and transport sperm and egg cells. Examples include the testes and penis in males and the ovaries and vagina in the female. The female body also can nurture developing offspring in the uterus. Moreover, hormones from the testes and ovaries promote the development of secondary sex characteristics in adults, including the facial hair of a man and the breasts and wide hips of a woman. - The reproductive system illustrates how the organ systems are, in a sense, not separate at all. Consider the uterus, the pear-shaped sac that houses the embryo and fetus. This organ consists mainly of muscle. It also contains nervous tissue, which is why a woman feels cramps when it contracts. Hormones from the endocrine system stimulate these contractions. The entire system is richly supplied with the circulatory system’s blood vessels, which also deliver the cells and chemicals of the immune system. 23.4 Organ System Interactions Promote Homeostasis - An animal’s body consists of mostly water. Some of this moisture makes up the cytoplasm inside every cell. The rest of it forms blood plasma and the i nterstitial fluid that bathes the body’s cells. - In the midst of this variability, an animal’s body must maintain its internal temperature, its blood pressure, and the composition of its fluids within certain limits. H omeostasis i s this state of internal stability. - All organisms maintain homeostasis. Without it, a body system may stop functioning, and the organism may die. - Many physiological mechanisms that maintain homeostasis use n egative feedback, in which a change in a condition triggers actions that reverses the change. - In all negative feedback systems, sensors monitor changes in some parameter. If the value is too high or too low, the system responds by counteracting the original change. In the body, the “supervisor” that coordinates much of the action is an almond-sized part of the brain called the hypothalamus. If blood pressure rises too high, for example, receptors in the walls of blood vessels signal the hypothalamus to slow the contraction of the heart The pressure drops. If blood pressure falls too low, the hypothalamus signals the heart to speed up, sending out more blood. - Only a few biological functions demonstrate p ositive feedback, in which the body reacts to a change by amplifying it. Blood clotting and childbirth are examples of positive feedback - once started, they perpetuate activity. By itself, positive feedback therefore does not maintain homeostasis. Ultimately, however, other controls cut off the positive feedback loop and restore equilibrium.
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