Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 41 , or fibrocartilage, has little ground substance, and its matrix is dominated by densely interwoven collagen fibers, making this tissue durable and tough. Pads of fibrous cartilage lie between the spinal vertebrae, between the pubic bones of the pelvis, around tendons, and within or around joints. In these positions, fibrous cartilage resists compression, absorbs shocks, and prevents damaging bone-to-bone contact. 4.3 Muscle Tissue There are three types of muscle tissue: skeletal, cardiac, and smooth muscle. Skeletal muscle forms the large muscles responsible for gross body movements and locomotion. Cardiac muscle is found only in the heart and is responsible for the circulation of blood. Smooth muscle , found in the walls of visceral organs and various other locations, provides elasticity, contractility, and support. of 368 Cartilage The matrix of cartilage is a firm gel that contains polysaccharide derivatives called chondroitin sulfates. Chondroitin sulfates form complexes with proteins in the ground substance, producing proteoglycans. Cartilage cells, or chondrocytes, are the only cells in the cartilage matrix. They occupy small chambers known as lacunae (lacus, lake). The physical properties of cartilage depend on the proteoglycans of the matrix and the type and abundance of extracellular fibers. Unlike other connective tissues, cartilage is avascular; thus, all exchange of nutrients and waste products must occur by diffusion through the matrix. Cartilage grows by two mechanisms: interstitial growth and appositional growth. In interstitial growth, chondrocytes in the cartilage matrix undergo cell division, and the daughter cells produce additional matrix. This process enlarges the cartilage internally. Interstitial growth is most important during development. The process begins early in embryonic development and continues through adolescence. In appositional growth, new layers of cartilage are added to the surface. In this process, cells of the inner layer of the perichondrium undergo repeated cycles of division. The innermost cells then differentiate into immature chondrocytes and produce cartilage matrix. As they become surrounded by and embedded in new matrix, they differentiate into mature chondrocytes. Appositional growth gradually increases the size of the cartilage by adding to its outer surface. Types of Cartilage The body contains three major types of cartilage: hyaline, elastic, and fibrous cartilage. • H ali e cartilag is the most common type of cartilage. Except inside joint cavities, a dense perichondrium surrounds hyaline cartilages. The matrix of hyaline cartilage contains closely packed collagen fibers that make it tough but somewhat flexible. Examples in adults include the connections between the ribs and the sternum, the nasal cartilages, and the supporting cartilages along the conducting passageways of the respiratory tract. • Elastic cartilage contains numerous elastic fibers that make it extremely resilient and flexible. These cartilages usually have a yellowish color on gross dissection. Elastic cartilage forms the external flap of the outer ear, the epiglottis, a passageway to the middle ear cavity, and small cartilages in the larynx. • Fibrous cartilage