Anatomy and Physiology - Study Questions: Bone Tissues

What are the different types of bones, and what are examples of each?

• Long Bones, such as the femur and humerus

• Short Bones, such as the carpals and tarsals

• Flat Bones, such as the scapula and pelvis

• Irregular Bones, such as the vertebrae and mandible

What are the different types of bone cells, and what do they do?

• Osteogenic cells - These are the stem cells in bones, and they have the ability to develop into other types of bone cells.

• Osteoblasts - These are responsible for bone formation.

• Osteocytes - These are mature bone cells and maintain the bone matrix.

• Osteoclasts - These cells break down bone tissue, a process known as bone resorption.

• Bone lining cells - These cells cover bone surfaces and are thought to play a role in the maintenance of the bone.

What's inside a flat bone?

Flat bones, like the scapula or pelvis, consist of a layer of spongy bone (also known as cancellous or trabecular bone) sandwiched between two thin layers of compact bone (also known as cortical bone). The spongy bone layer houses red bone marrow, which is responsible for blood cell production.

What's inside a long bone?

A long bone consists of a central shaft, known as the diaphysis, and two ends, known as epiphyses. The diaphysis is made of compact bone and contains a medullary cavity filled with yellow bone marrow, which is mainly composed of fat cells. The epiphyses are made of spongy bone, which contains red bone marrow responsible for blood cell production.

How do long bones grow?

Long bones grow in length due to the activity in the epiphyseal plate, a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side of the growth plate, cartilage is formed and pushed towards the older cells near the diaphysis where it is ossified. Over time, this process results in an increase in the length of the bone. Once the individual reaches maturity, the growth plates close and are replaced by bone, stopping further growth in length.

How do flat bones grow?

Flat bones grow through a process called intramembranous ossification. This process involves the transformation of mesenchymal tissue, a type of embryonic tissue, into bone. It begins with the differentiation of mesenchymal cells into osteoprogenitor cells, which then become osteoblasts. These osteoblasts produce bone matrix and eventually become trapped within it, turning into osteocytes, the mature bone cells. The formation of flat bones, such as the skull and clavicle, is primarily completed before birth, but bone remodeling continues throughout life.

What are the ostea inside long bones, and what is their function?

Osteons are the structural units of compact bone in long bones. They consist of lamellae surrounding a central Haversian canal, which carries the bone's blood supplies and nerve fibers. Osteons are aligned parallel to the bone's long axis, enhancing its strength and resistance to bending or fracturing. They also facilitate nutrient delivery and waste removal.

How do bones develop?

Bones form through ossification, which includes Intramembranous and Endochondral types. Intramembranous ossification transforms mesenchymal tissue into bone, creating flat bones like the skull. Endochondral ossification replaces hyaline cartilage with bone, forming most body bones. These processes start in fetal development and continue until adolescence.

What are different ways that bones break, and how do bones repair themselves after a fracture?

1. Greenstick fracture: is a type of bone break common in children where the bone bends and cracks, but doesn't break completely.

2. Spiral fracture: caused by a twisting motion

3. Comminuted fracture: where the bone breaks into multiple pieces, common in older people

4. Depression fracture: occurs in flat bones; is when a part of the bone gets pushed inward.

5. Growth plate fracture: when the bone breaks on the epiphyseal plate in children

6. Compound fracture: the bone breaks and penetrates the skin, risking infection.

The process of bone repair involves several stages. First, a blood clot forms at the site of the break to stop bleeding, known as a fracture hematoma. Then, a soft callus made of collagen and fibrocartilage forms around the fracture. This callus later hardens into a bony callus as new bone starts to form. Finally, the bony callus is remodeled over time, with excess bone being resorbed and the repaired bone being restored to its original shape.

How does the body control the amount of calcium in the blood?

The body controls the amount of calcium in the blood through the parathyroid hormone (PTH) and calcitonin. When calcium levels in the blood drop below normal, the parathyroid glands secrete PTH, which stimulates osteoclasts to break down bone tissue and release calcium into the bloodstream. PTH also increases the kidneys' reabsorption of calcium and stimulates the production of vitamin D, which helps the intestines absorb calcium. Conversely, when calcium levels in the blood are too high, the thyroid gland releases calcitonin, which inhibits the activity of osteoclasts, slowing the breakdown of bone tissue and reducing the amount of calcium released into the bloodstream.

What are the different types of cartilage, and where are they located?

1. Hyaline cartilage: This is the most common type and is found in the nose, trachea, and at the ends of long bones where it acts as a shock absorber in the joints.

2. Elastic cartilage: This type is found in the ear and the epiglottis, providing structure and maintaining shape while being flexible.

3. Fibrocartilage: This is the strongest type and is found in areas of the body under high stress like the intervertebral discs in the spine and the menisci in the knee.