Skeletal Physiology

10. Examples of hyaline cartilage: articular surfaces of synovial joints, trachea and larynx, and ventral ends of ribs.

Examples of elastic cartilage: larynx, epiglottis, and pinna of ear.

Examples of fibro cartilage: intervertebral disks, ligament and tendon to bone attachment sites, pubic symphysis, and intro-articular menisci.

Hyaline cartilage is easily distinguished from elastic and fibrocartilage because of the homogeneous (no fibers are visible) extracellular matrix (ECM) . The darker staining matrix immediately surrounding the capsule is called territorial matrix , while the matrix that occupies the majority of space between chondrocytes is interterritorial matrix .

Elastic cartilage (like hyaline cartilage) has chondrocytes located in lacunae and the tissue is surrounded by a perichondrium . Elastic fibers predominate in the ECM. The abundance of elastic fibers gives the ECM a heterogeneous (fibrillar) appearance when stained with H & E.

Fibrocartilage is intermediate in appearance between dense connective tissue and hyaline cartilage. Chondrocytes are situated in lacunae and no identifiable perichondrium is present. The matrix is acidophilic because of the large amount of coarse type I collagen fibers . Note that there are relatively few cells when compared with hyaline cartilage.

11. Cartilage:

A. Principle cell= chondrocytes

B. Principle cell= Type II

C. Major ground substance GAGs= keratin, chondroiton sulfates

Common Elements of all types of cartilage: 

Cell, fibers, and ground substances

Mechanisms of cartilage growth: modulation of balance between proteoglycan and collagen in vitro using chondroitinase ABC.

Bone functions: 

- support framework

-rigid lever

-protection

-source of minerals

Bone tissue must be added below the joint somewhere along the length of the bone. This occurs at the epiphyseal plate, or growth plate. Herechondrocytes first produce hyaline cartilage. The cartilage then becomes calcified or ossified to form hard bone tissue (involves addition of Ca+ and Phosphorous ions). The condrocytes produce cartilage on one side of the plate and push the end of the bone up. The other side of the epiphyseal plate gradually becomes calcified.

12.

Structural classification is based on the materials that hold the joint together and whether or not a cavity is present in the joint. There are three structural classes:

1.     Fibrous joints are held together by fibrous connective tissue. 

2.     Cartilaginous joints are held together by cartilage (hyaline or fibrocartilage). 

3.     Synovial joints are characterized by a synovial cavity (joint cavity) containing synovial fluid. 

Functional classification is based on the degree to which the joint permits movement. There are three types:

·         A synarthrosis joint permits no movement. Structurally, it may be a fibrous or cartilaginous joint.

·         An amphiarthrosis joint permits only slight movement. Structurally, it may be a fibrous or cartilaginous joint.

·         A diarthrosis joint is a freely movable joint. Structurally, it is always a synovial joint.

·         13. abduction: movement away from the mid-line of the body. Example: the arm is pulled away from the center of the body.

·         adduction: movement toward the mid-line of the body. Example: right femur extended out to the right side, inwards towards or across the centre of the body.

·         extension: straightening limbs at a joint. Example: extending the flexed (bent) elbow.

·         flexion: bending the limbs at a joint. Example: clenching a hand into a fist

·         rotation: a circular movement around a fixed point. Example: the shoulder or hip would point the toes or the flexed forearm inwards

1.  Broken bones in the spine-vertebral fractures- are the most common type of fracture. It is vertebral fractures that make man older women appear stooped. A broken hip-hip fracture- is the most severe. The major functions of the vertebral column are protection of the spinal cord, provides stiffening for the body and attachment for the pectoral and pelvic girdle, provides motion for the human skeleton, and transmits body weight in walking and standing. The functions of the hip is to provide stability for weight bearing such as standing, walking, or running, to allow mobility of the leg in space, and to transmit the loads from the upper body to the thigh and then to the lower leg.

2. The epiphyseal plate plays a major role in the elongation of long bones in Infants and adolescents, in adults who have stopped growing the plate is replaced by an epiphyseal line. A fracture along the epiphyseal plate in a child or adolescent could result in impeded growth and growth defects. In later life arthritis would be apparent in the joint where the fracture happened.

3. Changes in posture and gait (walking pattern) are common with aging as changes in the skin and hair. Bone mass or density is lost as people age, especially in women after menopause. The bones lose calcium and other minerals. The middle of the body (trunk) becomes shorter as the disks gradually lose fluid and become thinner. vertebrae lose some of their mineral content, making each bone thinner. The spinal column becomes curved and compressed (packed together). Bone spurs, caused by aging and overall use of the spine, may also form on the vertebrae. The joints become stiffer and less flexible. Inflammation, pain, stiffness, and deformity may result from breakdown of the joint structures. Bones become more brittle and may break more easily. Strength and endurance change. Loss of muscle mass reduces strength. Older people become tired more easily, and have less energy.