Chapter 3: Cell and Tissue PDF

Chapter 3 Cell and Tissue Prepared by Ms. Fatima Al Hamadani  Learning Objectives Name the concepts of cell theory Name the four elements of living matter Define cell and identify the three major cell regions. List the structures of the nucleus and explain its function. De...

Chapter 3 Cell and Tissue Prepared by Ms. Fatima Al Hamadani  Learning Objectives Name the concepts of cell theory Name the four elements of living matter Define cell and identify the three major cell regions. List the structures of the nucleus and explain its function. Describe the chemical composition of the plasma membrane and relate it to membrane function Describe the different cytoplasmic organelles and their major functions Loose Connective Tissues Loose connective tissues are softer and have more cells and fewer fibers than any other connective tissue type except blood. There are three main types of loose connective tissue: areolar, adipose, and reticular.  Areolar connective tissue Is a soft, pliable, “cobwebby” tissue that cushions and protects the body organs it wraps It functions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and in their proper positions. Soft layer of areolar connective tissue called the lamina propria  Areolar connective tissue Areolar connective tissue provides a reservoir of water and salts for the surrounding tissues, and essentially all body cells obtain their nutrients from and release their wastes into this “tissue fluid.” During inflammation, the local areolar tissue soaks up the excess fluid like a sponge, and the area swells and becomes puffy, a condition called edema  Adipose Connective Tissue It is an areolar tissue in which adipose (fat) cells predominate A glistening droplet of oil occupies most of a fat cell’s volume and compresses the nucleus, displacing it to one side. Adipose tissue forms the subcutaneous tissue beneath the skin, where it insulates the body and protects it from bumps and extremes of both heat and cold  Adipose Connective Tissue Adipose tissue also protects some organs individually: kidneys are surrounded by a capsule of fat Adipose tissue cushions the eyeballs in their sockets. There are also fat “depots” in the body, such as the hips, breasts, and belly, where fat is stored and available for fuel if needed Reticular connective tissue Consists of a delicate network of interwoven reticular fibers associated with reticular cells. It forms the stroma (literally, “bed” or “mattress”), or internal framework of an organ. The stroma can support many free blood cells (largely white blood cells called lymphocytes) in lymphoid organs such as lymph nodes, the spleen, and bone marrow  Blood It consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma The “fibers” of blood are soluble proteins that become visible only during blood clotting. Blood is the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, white blood cells, and many other substances throughout the body.  Muscle Cell Highly specialized to contract, or shorten, which generates the force required to produce movement. There are three types of muscle tissue: skeletal, cardiac, and smooth  Skeletal Muscle Packaged by connective tissue sheets into organs called skeletal muscles, which are attached to the skeleton. These muscles, which can be controlled voluntarily When the skeletal muscles contract, they pull on bones or skin. As a result, gross body movements or changes in our facial expressions occur. The cells of skeletal muscle are long, cylindrical, and multinucleate, and they have obvious striations (stripes).  Cardiac Muscle Is found only in the heart wall. As it contracts, the heart acts as a pump to propel blood through the blood vessels. Cardiac muscle has striations, but cardiac cells have only a single nucleus and are relatively short, branching cells that fit tightly together (like clasped fingers) at junctions called intercalated discs These intercalated discs contain gap junctions that allow ions to pass freely from cell to cell Cardiac Muscle Cardiac muscle is under involuntary control, which means that we cannot consciously control the activity of the heart. Smooth Muscle Has no striations, a single nucleus and are tapered at both ends. Smooth muscle is found in the walls of hollow organs such as the stomach, uterus, and blood vessels. Smooth Muscle As smooth muscle in its walls contracts, the cavity of an organ alternately becomes smaller (constricts when smooth muscle contracts) or enlarges (dilates when smooth muscle relaxes) so that substances are mixed and/or propelled through the organ along a specific pathway Smooth muscle contracts much more slowly than the other two muscle types, and these contractions tend to last longer. Peristalsis is a wavelike motion that keeps food moving through the small intestine, is typical of its activity  Nerve Tissue Comprised primarily of neurons. Function of Neurons: Receive and conduct electrochemical impulses throughout the body. Major functional characteristics: Irritability: Ability to respond to stimuli. Conductivity: Ability to transmit impulses.  Nerve Tissue Structure of Neurons: Their cytoplasm is drawn out into long processes (extensions), as long as 3 feet or more in the leg, which allows a single neuron to conduct an impulse to distant body locations. the nervous system is more than just neurons. A special group of supporting cells called neuroglia insulate, support, and protect the delicate neurons in the structures of the nervous system—the brain, spinal cord, and nerves. Tissue Repair Intact physical barriers such as the skin and mucous membranes, cilia, and the strong acid produced by stomach glands are just three examples of body defenses exerted at the tissue level. When tissue injury does occur, it stimulates the body’s inflammatory and immune responses, and the healing process begins almost immediately. Tissue Repair Tissue repair, or wound healing, occurs in two major ways: Regeneration Is the replacement of destroyed tissue by the same kind of cells Fibrosis involves repair by dense (fibrous) connective tissue, that is, by the formation of scar tissue. Which occurs depends on: (1) the type of tissue damaged (2) the severity of the injury. Tissue Repair Tissue injury sets the following series of events into motion: Inflammation Sets - Injured tissue cells release inflammatory the Stage chemicals. - Capillaries become more permeable, allowing fluid and clotting proteins to seep into the area. - Clot forms to stop blood loss and hold wound edges together. - Injured area is walled off to prevent the spread of bacteria or harmful substances. - Clot exposed to air dries and hardens, forming a scab.  Tissue Repair 2. Granulation Tissue Forms - Delicate pink tissue composed mainly of new capillaries grows into the damaged area from undamaged blood vessels. - Capillaries are fragile and may bleed easily. - Contains phagocytes that dispose of the blood clot. - Connective tissue cells (fibroblasts) produce collagen fibers to bridge the gap. 3. Regeneration and Fibrosis - Surface epithelium regenerates and grows between granulation tissue and the scab. - The scab detaches as healing progresses. - Final result: fully regenerated epithelium covering an area of fibrosis (scar). - Scar may be invisible or visible as a thin white line, depending on wound severity. Tissue Repair Tissues that regenerate easily: Epithelial tissue Fibrous connective tissue and bone Tissues that regenerate poorly: Skeletal muscle Tissues that are replaced largely with scar tissue: Cardiac muscle Nervous tissue within the brain and spinal cord