Chapter 5 - Section 5.3 - Study Guide - Assess Your Learning Outcomes - Page 173: 8

**Cartilage** is a type of connective tissue characterized by a firm, flexible matrix composed of collagen fibers and a gel-like ground substance. It provides structural support, cushioning, and flexibility to various parts of the body. Cartilage has several defining characteristics as a class: **Defining Characteristics of Cartilage:** 1. **Avascular:** Cartilage is avascular, meaning it lacks blood vessels. Nutrients and oxygen diffuse through the matrix, which limits its ability to repair and regenerate. 2. **Chondrocytes:** Chondrocytes are the specialized cells found within cartilage tissue. They are responsible for maintaining the cartilaginous matrix. 3. **Matrix:** The matrix of cartilage consists of collagen fibers (mainly type II collagen) embedded in a gel-like ground substance rich in proteoglycans. This composition provides strength, flexibility, and resistance to compression. 4. **Flexibility:** Cartilage is flexible and resilient, allowing it to withstand mechanical stress and distribute loads. There are three main types of cartilage in the human body, each with distinct histological characteristics, functions, and locations: **1. Hyaline Cartilage:** - **Histology:** Hyaline cartilage has a smooth, glassy appearance under the microscope. It contains fine collagen fibers evenly distributed in the matrix. - **Function:** Hyaline cartilage provides support and flexibility to the skeleton, particularly at joints. It also forms the embryonic skeleton and supports the respiratory passages. - **Location:** Found in the articular surfaces of bones, the nasal septum, the tracheal rings, and the costal cartilages (connecting ribs to the sternum). **2. Elastic Cartilage:** - **Histology:** Elastic cartilage contains a dense network of elastic fibers in addition to collagen fibers. This gives it a more elastic appearance. - **Function:** Elastic cartilage is highly flexible and provides support while maintaining shape. It can bend and recoil. - **Location:** Predominantly found in the external ear (auricle), the epiglottis (a flap that covers the trachea during swallowing), and the larynx (voice box). **3. Fibrocartilage:** - **Histology:** Fibrocartilage has a dense matrix with thick collagen fibers arranged in bundles, giving it a fibrous appearance. - **Function:** Fibrocartilage is highly durable and designed to resist compression and absorb shock. It provides support and stability at specific sites. - **Location:** Found in the intervertebral discs (between the vertebrae), the pubic symphysis (joint between the pubic bones), and certain tendons (e.g., the knee meniscus). **Perichondrium:** The perichondrium is a dense connective tissue layer that surrounds most cartilage types. It serves several important functions: - It contains blood vessels that supply nutrients and oxygen to the chondrocytes. - It acts as a source of new chondroblasts, which can differentiate into chondrocytes to aid in cartilage growth and repair. - It provides mechanical support and protection to the cartilage. **Where the Perichondrium is Absent:** The perichondrium is typically absent in areas where cartilage interfaces with other tissues or where it needs to interact more directly with surrounding structures. For example, articular cartilage at the ends of long bones lacks a perichondrium to allow for smooth articulation within joints. Similarly, fibrocartilage in intervertebral discs lacks a perichondrium to facilitate its connection to adjacent vertebrae. In these locations, the absence of a perichondrium allows for better integration with neighboring tissues.

**Cartilage** is a type of connective tissue characterized by a firm, flexible matrix composed of collagen fibers and a gel-like ground substance. It provides structural support, cushioning, and flexibility to various parts of the body. Cartilage has several defining characteristics as a class: **Defining Characteristics of Cartilage:** 1. **Avascular:** Cartilage is avascular, meaning it lacks blood vessels. Nutrients and oxygen diffuse through the matrix, which limits its ability to repair and regenerate. 2. **Chondrocytes:** Chondrocytes are the specialized cells found within cartilage tissue. They are responsible for maintaining the cartilaginous matrix. 3. **Matrix:** The matrix of cartilage consists of collagen fibers (mainly type II collagen) embedded in a gel-like ground substance rich in proteoglycans. This composition provides strength, flexibility, and resistance to compression. 4. **Flexibility:** Cartilage is flexible and resilient, allowing it to withstand mechanical stress and distribute loads. There are three main types of cartilage in the human body, each with distinct histological characteristics, functions, and locations: **1. Hyaline Cartilage:** - **Histology:** Hyaline cartilage has a smooth, glassy appearance under the microscope. It contains fine collagen fibers evenly distributed in the matrix. - **Function:** Hyaline cartilage provides support and flexibility to the skeleton, particularly at joints. It also forms the embryonic skeleton and supports the respiratory passages. - **Location:** Found in the articular surfaces of bones, the nasal septum, the tracheal rings, and the costal cartilages (connecting ribs to the sternum). **2. Elastic Cartilage:** - **Histology:** Elastic cartilage contains a dense network of elastic fibers in addition to collagen fibers. This gives it a more elastic appearance. - **Function:** Elastic cartilage is highly flexible and provides support while maintaining shape. It can bend and recoil. - **Location:** Predominantly found in the external ear (auricle), the epiglottis (a flap that covers the trachea during swallowing), and the larynx (voice box). **3. Fibrocartilage:** - **Histology:** Fibrocartilage has a dense matrix with thick collagen fibers arranged in bundles, giving it a fibrous appearance. - **Function:** Fibrocartilage is highly durable and designed to resist compression and absorb shock. It provides support and stability at specific sites. - **Location:** Found in the intervertebral discs (between the vertebrae), the pubic symphysis (joint between the pubic bones), and certain tendons (e.g., the knee meniscus). **Perichondrium:** The perichondrium is a dense connective tissue layer that surrounds most cartilage types. It serves several important functions: - It contains blood vessels that supply nutrients and oxygen to the chondrocytes. - It acts as a source of new chondroblasts, which can differentiate into chondrocytes to aid in cartilage growth and repair. - It provides mechanical support and protection to the cartilage. **Where the Perichondrium is Absent:** The perichondrium is typically absent in areas where cartilage interfaces with other tissues or where it needs to interact more directly with surrounding structures. For example, articular cartilage at the ends of long bones lacks a perichondrium to allow for smooth articulation within joints. Similarly, fibrocartilage in intervertebral discs lacks a perichondrium to facilitate its connection to adjacent vertebrae. In these locations, the absence of a perichondrium allows for better integration with neighboring tissues.