How Old Is Baby When Their Skeleton Is Fully Formed

Development of the Skeleton

Early in gestation, a fetus has a cartilaginous skeleton that becomes bone in the gradual process of endochondral ossification.

Learning Objectives

Compare and contrast osteogenesis by intramembranous and endochondral ossification

Key Takeaways

Cardinal Points

• At birth, a newborn babe has over 300 bones, while on average an adult homo has 206 bones.
• Ossification or osteogenesis is the procedure of generating new bone material past precursor cells called osteoblasts.
• Two processes result in the formation of normal, healthy bone tissue: intramembranous ossification and endochondral ossification.
• Intramembranous ossification is the direct laying of os into the archaic connective tissue (mesenchyme). The membrane that occupies the place of the future bone resembles connective tissue and ultimately forms the periosteum. It is composed of fibers and granular cells in a matrix.
• Endochondral ossification involves cartilage which is then mineralized.
• Bones are dynamic structures that respond to practical force over fourth dimension. With chronic weight begetting and the forces from daily apply and movement, os mass tin can exist maintained or increased.

Key Terms

• intramembranous ossification: Production of bone tissue during fetal development without a cartilage template. The membrane that occupies the identify of the future bone resembles connective tissue and ultimately forms the periosteum, or outer bone layer.
• trabecula: A modest, mineralized spicule that forms a network in spongy bone.
• mesenchyme: Undifferentiated cells of the early embryo that develop into the tissues of the lymphatic and circulatory systems, as well as connective tissues throughout the body such as os and cartilage.
• endochondral ossification: The process by which bone tissue is created using a cartilage template during fetal development.

Early in gestation, a fetus has a cartilaginous skeleton from which the long bones and most other bones gradually form throughout development and for years afterwards birth in a process called endochondral ossification. Ossification or osteogenesis is the process of laying new os textile by cells called osteoblasts. Two processes result in the formation of normal, good for you bone tissue. Intramembranous ossification is the direct laying of os into the primitive connective tissue (mesenchyme). This is how the flat bones of the skull and the clavicles are formed. Endochondral ossification involves cartilage as a precursor. Ossification of the mandible occurs in the fibrous membrane roofing the outer surfaces of Meckel's cartilages.

Endochondral Ossification: The development of the primary and secondary ossification centers

Intramembranous Ossification

In bones developed in membrane, no cartilaginous mold precedes the appearance of the bony tissue. The membrane that occupies the place of the future bone resembles connective tissue and ultimately forms the periosteum; it is equanimous of fibers and granular cells in a matrix. The peripheral portion is more fibrous, while in the interior the cells or osteoblasts predominate. The whole tissue is richly supplied with blood vessels. As the osteogenetic fibers abound out to the periphery, they continue to lapidify and give rising to fresh bone spicules. Thus, a network of bone is formed, the meshes of which contain the blood vessels and a fragile connective tissue crowded with osteoblasts. Osteoblasts add layers of fresh bone to the trabeculae. These layers subsequently encroach upon the mesh, under the periosteum, and around the larger vascular channels that become the Haversian canals, thickening and developing the bones.

Endochondral Ossification

The perichondrium becomes the periosteum, which contains a layer of undifferentiated cells (osteoprogenitor cells) that subsequently become osteoblasts. These osteoblasts secrete osteoid confronting the shaft of the cartilage model that serves as support for the new bone. Chondrocytes in the primary center of ossification begin to grow (hypertrophy). They finish secreting collagen and other proteoglycans and brainstorm secreting alkaline metal phosphatase, an enzyme essential for mineral deposition. Then calcification of the matrix occurs and the hypertrophic chondrocytes brainstorm to die, creating cavities within the bone. The hypertrophic chondrocytes (before apoptosis) secrete vascular endothelial prison cell growth factor, which induces the sprouting of claret vessels from the perichondrium. Blood vessels forming the periosteal bud invade the cavity left by the chondrocytes and branch in opposite directions along the length of the shaft. The blood vessels carry hemopoietic cells, osteoprogenitor cells, and other cells within the cavity. The hemopoietic cells will later course the bone marrow. Osteoblasts, differentiated from the osteoprogenitor cells that entered the cavity via the periosteal bud, apply the calcified matrix as a scaffold and begin to secrete osteoid, which forms the bone trabecula. Osteoclasts, formed from macrophages, interruption down spongy bone to form the medullary (bone marrow) cavity.

Crumbling and the Skeleton

In osteoporosis, os mineral density (BMD) is reduced and the integrity of bone proteins is contradistinct, increasing the take a chance of fracture.

Learning Objectives

Construct a diagnosis and handling programme for osteoporosis

Primal Takeaways

Central Points

• The risk of osteoporosis tin be reduced with lifestyle changes and sometimes medication, both aimed at restoring the amounts and types of necessary bone-associated proteins.
• Osteoporosis itself has no symptoms; its main effect is the increased risk of bone fractures.
• Treatments for osteoporosis include changes in nutrition and exercise, increased consumption of calcium and vitamin D, and prescriptions for bisphosphonates.

Key Terms

• bisphosphonates: A class of drugs that prevents the loss of os mass, used to care for osteoporosis and like diseases. They are the virtually commonly prescribed drugs used to treat osteoporosis.
• bone mineral density: Abbreviated BMD, the corporeality of mineral thing per foursquare centimeter of os. BMD is used in medicine as an indirect indicator of osteoporosis and fracture risk.
• osteoporosis: A disease in which the bones go extremely porous and are discipline to fracture most common in mail service-menopausal women.

Osteoporosis is a bone illness that leads to an increased risk of fracture. In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture deteriorates, and the corporeality and variety of proteins in bone is altered.

Types of Osteoporosis

(a) Osteoporotic Fractures and (b) Woman with Osteoporosis: Image shows compression fractures of the lumbar spine. Hyperkyphosis, colloquially called a "dowager'southward hump," refers to an anteriorly concave curvature of the thoracic region of the spine.

The disease may be classified every bit master type 1, primary type ii, or secondary. The class of osteoporosis virtually mutual in women after menopause is referred to every bit primary type 1 or postmenopausal osteoporosis.

Master blazon ii osteoporosis or senile osteoporosis occurs after age 75 and is seen in both females and males at a ratio of two to one. Finally, secondary osteoporosis may arise at whatsoever age and bear upon men and women equally. This form of osteoporosis results from chronic illness or prolonged employ of medications such as glucocorticoids. Osteoporosis affects 55% of Americans aged 50 and above. Of these, approximately 80% are women.

Symptoms

Osteoporosis itself has no symptoms; its main consequence is the increased take chances of fractures caused by weakened bones. Osteoporotic fractures, chosen fragility fractures, occur in situations where healthy people would not normally break a bone. These oftentimes affect the vertebral cavalcade, rib, hip, and wrist. The underlying mechanism in all cases of osteoporosis is an imbalance betwixt bone resorption and os formation.

Physical deformation tin occur secondary to compromised bone densities. One case is hyperkyphosis, colloquially called a "dowager's hump," which refers to an anteriorly concave curvature of the thoracic region of the spine.

Treatment

Osteoporosis risks can be reduced with lifestyle changes and sometimes medication. Lifestyle changes include diet, exercise, and autumn prevention. Exercises to tone deambulatory muscles and ameliorate proprioception are recommended to decrease gamble for falls. In add-on, the anabolic effect of practise tin sometimes prevent progression of osteoporosis. Medication includes calcium, vitamin D, and bisphosphonates.

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Source: https://courses.lumenlearning.com/boundless-ap/chapter/development-of-the-skeleton/

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