Chapter 7: Skeletal system components and functions General features of bone Bon

Question

Chapter 7:

Skeletal system components and functions

General features of bone

Bone cell functions: osteocyte, osteoblast, osteoclast

Bone matrix: organic and inorganic components

Structure/function/components of osteon (central canal, perforating canal, lacunae, lamella, etc.)

Differences between compact bone and spongy bone and general features of each

Compare/contrast intramembranous and endochondral ossification

Steps for endochondral ossification

Steps for bone repair and types of fractures

Examples of long, short, flat, irregular bones

Mechanisms of calcium homeostasis: hormones that regulate hypo and hypercalcemia

Explanation / Answer

Skeletal system components and functions

1) GENERAL FEATURES OF BONE

- Bones are the connective tissue mass that is made up of calcium phosphate and minerals.
- There are long, short, flat and irregural bones.
- It has epiphysis at as the rounded end of bones. It gives articulation site and the place for attachment of tendon and ligaments.
- The middle portion of bone is called diaphysis.
- Bones posses endosteum lining the internal marrow that covers spongy bones AND periosteum that is external sheath covering the bone.

Bone cell functions:

1) Osteocytes : They are secreted from osteoblasts, which is a bone forming cell and they continue to form the bone.

2) Osteoclasts : It facilitates bone resorption. It is a process by which osteoclass breaks bone tissue to trasfer calcium and minerals from bone to blood.

3) Osteoblasts : It facilitates the process of transfering calcium and minerals from blood to the bone matrix thus strengthening the bone.

Bone matrix: organic and inorganic components

Organic : Collagen , proteoglycans , matrix proteins , cytokine
- 40% of bone
inorganic : SALTS such as calcium hydroxyapatite , osteocalcium phosphate
- 60% of bone

Osteon

Structure :

- It is the fundamental functional unit of much compact bone.
- It is a cylindrical structure that had diameter of 0.2mm.

Components :

Function
- The major fuction is provision of a network supply to the matrix of bone which allows the intake of nutrients in the bone.

Types of bones:

1) Compact  

2) Spongy bones

Intramembranous and endochondral ossification

1) Intramembranous : Occurs in flat bones. Replace thin connective tissue with bone.
2)  Endochondral : Occurs in long, irregular and short bones. Replace fetal cartilage with bone

Steps for endochondral ossification

1) Resting chondrocytes
2) Proliferation of chondrocytes
3) Maturation and enlargement of condrocytes
4) Degeneration of chondrocytes and matrix calsification
5) Ossification : - Cavities invade vessles---------Osteoclasts digest cartilage--------Osteoblasts replaced with bone

Steps for bone repair and types of fractures

Steps for bone repair

Types of fracture

Examples of bones

Mechanisms of calcium homeostasis

Calcium homeostasis is the process of maintaining adequate calcium levels in body.
Defect in this mechanism may lead to hypocalcemia or hypercalcemia

- When the blood calcium level increases, thyroid gland secrets calcitonin.
- It allows the calcium to get deposited in the bone.

-When the blood calcium levels drops, Parathyroid glands secret pathyroid hormone.
- It acts upon the bone to remove calcium and transport it to the blood.

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