Describe the structure and development of bones and the skeleton and the factors that influence it.

National Diploma in Health and Social Care

Unit 32 Mobility and Exercise for Health and Social Care

P1,P2,M1 – Describe the structure and development of bones and the skeleton and the factors that influence it.

(A)Ossification

The skeleton is developed during foetal development; ossification is the name given to bone formation and happens in two ways which are Intramembranous and Endochondrial.

Intramembranous

Intramembranous ossification involves the replacement of sheet-like connective tissue membranes with bony tissue. Bones that are formed in this way are called Intramembranous bones. They include certain flat bones of the skull and some of the irregular bones. The future bones are first formed as connective tissue membranes.

Endochondrial

Endochondral ossification involves the replacement of hyaline cartilage with bony tissue. Most of the bones of the skeleton are formed in this way. These bones are called endochondral bones. In this process, the future bones are first formed as hyaline cartilage models. This is the type of bone formation found in the development of long bones such as the femur and humerus.

(B) Developing of the skeleton

During the first few weeks of conception, parts of the skeleton begin to form and by the end of the eighth week, the skeletal pattern is formed with cartilage and connective tissue membranes and ossification begins.

The development of bones continues throughout adulthood. It continues to develop for repair of fractures and the remodeling to meet the changes in lifestyle. Bone is made by cells called Osteoblast which is responsible for bone formation and Osteoclast which breaks down and reabsorbs bone.

Lengthening of bones and Closure of the epiphyses

Bones grow in length at the epiphyseal plate which is responsible for the lengthening of the diathesis, by a process which is similar to endochondral ossification. This continues throughout childhood and into adolescent years until the cartilage growth slows and finally stops. When cartilage growth ceases, the epiphyseal plate completely ossifies so that only a thin epiphyseal line remains and the bones can no longer grow in length. Bone growth is under the influence of growth hormone from the anterior pituitary gland and sex hormones from the ovaries and testes.

Development of the spinal curvatures

As we develop in the womb, our spine curved into a c- shape, as we develop and learn to lift our heads in the womb and when we eventually born curves can be seen in the neck. During the stages of develop as a baby, when we learn to crawl and walk, curves can be seen in the spine, until the spine develops into an S- shape or sigmoid shaped spine.

Calcium storage in the bones and the concept of dynamic state of bone

Calcium is a mineral that is stored in the bones. Nearly all the calcium in the body is stored in bone tissue. Our bodies absorb calcium from the calcium rich diet we eat. Calcium is constantly lost from the bones in our body as we age and grow and through general wear and tear on bones. The name for this process of losted calcium is called Dynamic movement of calcium mineral, in and out of bones.

Compact bone

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Calcium storage in the bones and the concept of dynamic state of bone

Compact bone

Compact bone is a type of consisting of closely packed or , and forms the extremely hard of . Because of the closely packed and stacked layers with few gaps on this , the compact bone is extremely hard and dense (compared with the ). These features of compact bone are vital to serve its function in providing support to the and protecting the . It also provides levers for movement and store (similar to ).

Cancellous bone

Cancellous bone is the tissue inside of that resembles a or a with spaces containing or . It is found at the ends of long and in the . It has low and strength but has high surface area that allows room for and . The outer surface layer of this contains the red where takes place.

Bones are classified according to their shape. There are 5 types of bone in the human skeleton which are:

One of the elongated of the , consisting of a (diaphysis) and two (epiphyses) usually wider than the shaft. The is composed of compact surrounding a central .

Short bone

Short bones have equal and consist of of enclosing and .

Irregualr bones

Irregular bones have or . This type of bone can not be grouped with bones in the body such as long or short.

Flat bones

Flat bones are used for protection or for broad surfaces of muscle. Flat bones are thin, flattened, and usually curved.

Sesamoid bone

Sesamoid bones are usually found where tendons pass over a joint, they protect the tendons and increase its mechanical effect. They can be found in the hands, feet and knee joints.

There are two types of bone marrow: red marrow which consisting mainly of and yellow marrow which consisting mainly of . , and most arise in red marrow. Both types of bone marrow contain numerous blood vessels and capillaries.

At birth, all bone marrow is primarily purple. With age, more and more of it is converted to the yellow type. About half of the bone marrow is red. Red marrow is found mainly in the , such as the , , , , and , and in the material at the ends of the such as the and . Yellow marrow is found in the hollow interior of the middle portion of long bones.

Cartilage is a type of connective tissue in the body. It is made of cells called chondrocytes embedded in a matrix, strengthened with fibers of collagen and sometimes elastin, depending on the type of cartilage. There are three different types: hyaline cartilage, elastic cartilage, and fibro cartilage. Cartilage serves to provide structure and support to the body's other tissues without being as hard or rigid as bone. It can also provide a cushioning effect in joints.

Hyaline cartilage makes up the majority of the body's cartilage. It lines the bones in joints, helping them to articulate smoothly.
Elastic cartilage is more flexible than the other types of cartilage because of the elastin fibers it contains. This type of cartilage is found in the outer ear. It provides the perfect balance of structure and flexibility and helps keep tubular structures open.
Fibro cartilage is the strongest and most rigid type of cartilage. It contains more collagen than hyaline cartilage. Fibrocartilage makes up the intervertebral discs, connects tendons and ligaments to bones, and appears in other high-stress areas.

Ligaments connect bones to each other over joints.

The skeleton is a framework of bones and cartilage providing four major functions for the body they are:

Protection-The skeleton provides protection for the bodies vital organs i.e. brain, heart and lungs and the spinal cord.
Shape & Support-The skeleton provides the shape and support that gives the body its shape.
Movement-Most of the bones are connected to other bones at flexible joints. The bones provide attachment for the tendons of the skeletal muscles and the ligaments of the joints.
Blood Production-Red blood cells, and some white cells , are manufactured by the bone marrow which is found in the cavities of some of the larger bones.

These are the main functions, but the skeleton also has the function of storing minerals such as calcium.

Bones of the Cranium

The human cranium and the facial bones are the foundation for the soft tissues of the face and head. These bones make up much of the visible appearance of the human face depends upon the shapes and qualities of these bones. The cranium is that part of the skull that holds and protects the brain in a large cavity, called the cranial vault.

The spine

The spine is made up of individual bones called vertebrae, which provide support for the spine. These vertebrae are connected in the front of the spine by intervertebral discs that help support the spine and also allow it to move.

The skeleton can be divided into two major areas which consisted of the Axial skeleton and the Appendicular skeleton.

The axial skeleton consists of 80 bones of the skeleton which are in the head and trunk of the human body. There five sections which are: the , the of the inner ear, the of the throat, the , and the .

The appendicular skeleton consists of the Shoulder girdle, Upper limb (arm, hand), Pelvic girdle, Lower limb (leg, foot).

(F) Types of joints

A joint is where two or bones join together. They are classified according to their structure or the movement they allow. There are three types of joint which are:

Fixed or fibrous (Synarthrosis) which have no movement such as the skull
Partically, semi moveable or cartilaginous (Amphiarthrosis) these can be found between the spinal vertebrae
Fully moveable, synovial (diarthosis), these type of joint can be subdivided into: ball and socket (shoulder or hip), hinge (knee or elbow), pivot (head or vertebral column), saddle (Thumb), gliding (between vertebra) and condyloid (wrist).

The following pictures show various joints:

Fibrous: A, syndesmosis (tibiofibular); B, suture (skull).
Cartilaginous: C, symphysis (vertebral bodies); D, synchondrosis (first rib and sternum).
Synovial: E, condyloid (wrist); F, gliding (radioulnar); G, hinge (elbow); H, ball and socket (hip); I, saddle (carpometacarpal of thumb); J, pivot (atlantoaxial).

(Taken from http://medical-dictionary.thefreedictionary.com/Joints+(anatomy))

National Diploma in Health Studies

Unit 32 Mobility and Exercise for Health and Social Care

Teacher: Sarah Cooper

Sarah-Jane Burke

M1 – (D) Influencing factors: Genetics, age, diet, weight, exercise and disease

Many things can influence someone’s bones when growing. The first thing which will influence grown is genetics. The most common genetic factor that influences bone growth and the most commonly known factor is Dwarfism. The most common cause of dwarfism is , which is a bone growth disorder, which is responsible for 70% of dwarfism cases. In cases of Achondroplasia, the limbs are disproportionally short compared to the trunk (abdomen area), with the head larger than normal, increased spinal curvature and unique facial characteristics, this is usually caused by one or more in bone or cartilage development. Achondroplasia is a mutation in the gene, which is an inhibitor that regulates bone growth. In cases of achondroplasia, the FGR3 gene is too aggressive, negatively impacting bone growth.

Bone mass or density is lost as people age, especially in women after . The bones lose calcium and other minerals. The spine is made up of bones called vertebrae. Between each bone is a gel-like cushion (intervertebral disk). The 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. Bones become more brittle and may break more easily. Overall height decreases as bones age.

Exercise is one of the best ways to slow or prevent problems with the muscles, joints, and bones. A moderate exercise program can help you maintain strength and flexibility. Exercise helps the bones stay strong. Exercising allows us to maintain muscle strength, coordination, and balance, which in turn helps to prevent falls and related fractures. This is especially important for older adults and people who have been diagnosed with osteoporosis.

A with adequate amounts of calcium is important. Women need to be especially careful to get enough calcium as they age. Fruits and vegetables contain vitamins and minerals such as vitamin D, calcium, phosphorus, and magnesium which are known to modulate skeletal health.

Weight is closely related to bone strength. In adults who are too fat, the bone density is high. If they are thin, the bone density is low. It is not advised to be overweight to obtain health bones, but it is important to avoid becoming too thin. Adults who lose weight lose bone density. Thin men and women are more likely to break bones when they are older. Boys and girls who are too thin will definitely have lower bone density. If they are too heavy, sometimes the bone density will be high. But if children are fat because they don't get any exercise, the bone density might be low and they might break their wrist more easily.

Osteoporosis is the most known disease of bone, the amount of bone decreased and the strength of trabecular bone is reduced, cortical bone and bones are susceptible to fracture. Osteoporosis is condition that features loss of the normal . Osteoporosis occurs most often in older people and in women after menopause. Rickets is another disease of the bone most people know about. It is an abnormal bone formation in children resulting from inadequate calcium in their bones. This lack of calcium can result from inadequate dietary calcium, inadequate exposure to sunshine (needed to make vitamin D), or from not eating enough vitamin D. Rickets is a failure to mineralize bone.