Skeletal physiology

Types of Cartilage

Cartilage• Cartilage is a specialized form of connective tissue

containing chondrocytes which secrete, and are surrounded by, an extensive intercellular matrix. Chondrocytes occur singly or in isogenous groups, composed of 2-8 cells derived by mitosis from a single chondrocyte. The cells are in the lacunae (cavities) within the matrix. Matrix stains more intensely immediately adjacent to the lacunae and the dark staining zone is called the capsule. The strength and durability of cartilage are properties of the matrix, which is an interlaced network of collagenous and/or elastic fibers in a ground substance, a gel of complex proteoglycans.

Three Types of Cartilage

• Hyaline cartilage is found lining articular surfaces, and in the nasal septum, tracheal rings, costal cartilages, and the epiphyseal cartilage of growing bone

• Elastic cartilage is found in the ear and epiglottis, where it provides a rigid but elastic, framework. Its principal components are elastic fibers but type II collagen is also present. Some elastic fibers may be present in the tracheal cartilage.

• Fibrocartilage is found in intervertebral discs, the pubic symphysis, in menisci of joints, and often occurs where tendon and ligament are joined to bones. Its appearance varies with its location. The major and characteristic intercellular component of this tissue consists of thick, interlaced collagenous fibers.

Mechanism of Growth Bone

• Bones grow longer over time but they also get thicker. There are mechanism that allow for bones to grow in both length and width.

• To make a bone longer just add bone tissue to the ends. If tissue is added at the end of the bone the skeleton could not move properly. It's like closing both lanes on an interstate until the bridge is repaired.

• Bone tissue must be added below the joint somewhere along the length of the bone. This occurs at the epiphyseal plate, or growth plate. Here chondrocytes first produce hyaline cartilage.

Cartilage• Cartilage forms from initial

condensation directly from mesenchyme and then grows by a combination of apositional growth

• Interstitial growth - Chondroblasts within the existing cartilage divide and form small groups of cells, isogenous groups, which produce matrix to become separated from each other by a thin partition of matrix. Interstitial growth occurs mainly in immature cartilage.

• Appositional growth - Mesenchymal cells surrounding the cartilage in the deep part of the perichondrium (or the chondrogenic layer) differentiate into chondroblasts. Appositional growth occurs also in mature cartilage.

Joints according to structure and function.

Hinge joint • Flexion/ extension. • Elbow and knee.

Pivot joint. • Rotation of one bone around another. • Neck.

Ball and socket joint. • Flexion, extension, abduction. • Shoulder and hip.

Saddle joint.• Flexion, extension, adduction, abduction,

circumduction. • Thumb.

Condyloid joint. • Flexion/Extension/Adduction/

Abduction/Circumduction.• Wrist joint.

Gliding joint. • Gliding movement. • Intercarpal joints.

Osteoporosis. • Osteoporosis is when bone density is decreased,

normally the process of matrix remodeling keeps bones at the correct density but Osteoporosis slows this down.

Cancer treatment and bone marrow• Cancer treatment can destroy bone marrow which

is where red blood cells are naturally replaced. Without the bone marrow patients are more susceptible to sickness. Bone marrow transplants replace the bone marrow with healthy normal marrow.

Intramembranous ossification: when cells of an embryo transforms into bone. In early development, the embryo has three cell layers: the ectoderm which is on the outside, mesoderm in the middle, and endoderm on the inside of the embryo. Bones of the skull come directly from the mesenchyme cells by intramembranous ossification. Endochondral ossification: this is the gradual replacement of cartilage by the bone. This process is responsible for forming most of the skeleton of vertebrates. Osteoblasts arise in regions of cartilage called ossification centers. (9)Intramembranous and Endochondral Development

1. Inflammation: in a bone fracture, white blood cells move in to the area to clean up debris created by the break. Inflammation triggers the growth new blood cells.2. Soft callus: as the blood cells divide and multiply near the break, the new blood vessels develop to fuel the repair process; the body also creates simply fibrous tissue cartilage around the bone fracture to bridge the gap.3. Hard callus: later on, the body replaces the soft callus with a hard callus, connecting the fragments of the bone more solidly. It creates a bulge at the site of the fracture.4. Remodeling: the body replaces the old bone with a new bone in a continual process called remodeling; it makes the bone stronger and compact and blood circulation in the bone improves.(8)

Steps in bone fracture repair

Steps in bone fracture repair

1 2

3 48

8

8

8

Bone: the types of bones are divided into long, short, irregular, flat, sesamoid and sutural bones. Their function is to protect the body from mechanical damage, to provide support, assist in movement, to store minerals, produce red blood and white blood cells, and to be the framework and shape for the body. The bones are made up of osteoblasts, osteocytes, osteoclasts, and bone lining cells. Cartilage: the types of cartilage are hyaline cartilage, fibrocartilage and elastic cartilage. The main functions is to reduce the friction at the joints, support tracheal and bronchial tubes, they act as shock absorbers between the vertebrae, also maintaining the shape and flexibility of ear, nose, along with others. Cartilage is made up of chondroblasts, chondrocytes, and dense matrix that is composed of collagen and elastic fibres. (10)Basic Structural units of Bones and Cartilages

Major Parts of The Haversain System

Main Parts•Haversian Canal •Lucanae•Canaliculi•Osteon•Periosteum•Lamellae•Trabeculae

Functions of Three Major Bone Cells• Osteoblasts- These are bone forming cells within the bone.

• Osteocytes- These are involved in the formation of the bone, maintenance of the matrix, and homeostasis of the calcium.

• Osteoclasts- The cells are responsible for bone resorption and remodeling.

Five Homeostatic Functions in Bones• Maintain shape and structure of the bone.• Strengthening the bone and adding tissue.• Remodeling broken bones.• Calcium from bones being used in other parts of

body.• Mineral reservoir, contains many minerals that the

body can use.

Types of bones

Long Bones• Femur,

Short Bones• Carpals

Irregular bones• vertebrae

Flat bones• Bones of the skull

Structures of a long bone

Types of bone tissue• Spongy• Compact

Compact bone

• Is made up of concentric rings of matrix that surround central canals which contain blood vessels.

• Embedded in this bone tissue are small cave-like spaces called lacunae, which are connected to each other through small tunnels called canalicula.

• The lacunae contain osteocytes cells. As just discussed, osteocytes help maintain healthy bone tissue and are involved in the bone remodeling process that will be outlined later in this lesson.

Spongy • Looks like an irregular latticework (or sponge) with

lots of spaces throughout. • These spaces are filled with red bone marrow

which is the site of hemopoesis or formation of blood cells

Changes in skeletal frame work• During the aging process, adults face the issue of

a changing skeletal framework. • As humans age, the force-generating capacity

(strength) of their skeletal muscles is reduced. As a result, many older people experience difficulty in performing their activities of daily living. The loss of force production in older people is primarily to the result of muscle atrophy and alterations in the percentage of contractile tissue within muscle rather than deficits in muscle.

An image depicting growth plate fractures can be seen below.

In growing children, sprains and strains often result in potentially serious growth plate fractures and physeal fractures. These same sprains and strains in active adults are relatively benign injuries. This article discusses some of the important orthopedic history relative to the physes, relevant anatomy, classification systems, and some details of physeal fractures in specific areas of the body.

Growth plate fractures

fractures

• Growth plate (physeal) fractures. Clinical appearance of the knee of a patient with a minimally displaced Salter-Harris I fracture of the distal femur. Impressive swelling was noted adjacent to the joint, but no evidence of intra-articular swelling was present. The patient was markedly tender to palpation about the distal femoral physis.