Cardiac Muscle TissueThe cardiac muscle cells are striated and are joinedend to end, resulting in a complex network ofinterlocking cells (fig. 1-11). Cardiac muscles areinvoluntary muscles and are located only in the heart.These tissues are responsible for pumping bloodthrough the heart chambers and into certain bloodvessels.NERVE TISSUENerve tissue is the most complex tissue in thebody. It is the substance of the brain, spinal cord, andnerves. Nerve tissue requires more oxygen andnutrients than any other body tissue. The basic cell ofthe nerve tissue is the neuron (fig. 1-12). This highlyspecialized cell receives stimuli from, and conductsimpulses to, all parts of the body.ORGANSLEARNING OBJECTIVE:Recall howorgans and body systems are composed of twoor more kinds of tissue that perform specializedfunctions within the body.As a group of similar cells forms tissues, two ormore kinds of tissues grouped together and performingspecialized functions constitute an organ. Organs aregrouped together to form systems (such as the urinarysystem, composed of the kidneys, ureters, bladder, andurethra).THE SKELETAL SYSTEMLEARNING OBJECTIVE:Identify theparts of bone and their functions.The skeleton, the bony framework of the body, iscomposed of 206 bones (fig. 1-13). It supports andgives shape to the body; protects vital organs; andprovides sites of attachment for tendons, muscles, andligaments. The skeletal bones are joined members thatmake muscle movement possible.ANATOMY OF BONESOsteology is the study of the structure of bone.Bone is made up of inorganic mineral salts (calciumand phosphorus being the most prevalent) and anorganic substance called ossein. If human bones weresoaked in dilute acid until all inorganic mineral saltswere washed out, all that would remain would be aflexible piece of tissue that could be easily bent andtwisted. Inorganic mineral salts give bone its strengthand hardness.Bone consists of a hard outer shell, called compactbone, and an inner spongy, porous portion, calledcancellous tissue (fig. 1-14). In the center of the boneis the medullary canal, which contains marrow.There are two types of marrow, red and yellow. Yellowmarrow is ordinary bone marrow in which fat cellspredominate. It is found in the medullary canals andcancellous tissue of long bones. Red marrow is one ofthe manufacturing centers of red blood cells and isfound in the articular ends of long bones and incancellous tissue.At the ends of the long bones is a smooth, glossytissue that forms the joint surfaces. This tissue is calledarticular cartilage because it articulates (or joins)with, fits into, or moves in contact with similarsurfaces of other bones. The thin outer membranesurrounding the bone is called the periosteum. Animportant function of the periosteum is to supplynourishment to the bone. Capillaries and blood vesselsrun through the periosteum and dip into the bonesurface, supplying it with blood and nutrients. The1-6HM3F0112AXONDENDRITESCELL BODYFigure 1-12.—Neuron.HM3F0111Figure 1-11.—Cardiac muscle tissue.
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