Skeletal System

Question 1

Bony tissue structure

Answer 1

Extracellular matrix between spaced out bone cells.

Question 2

Describe the 5 bone shapes

Answer 2

1. Long bones = Greater in length than width (humerus).
2. Short bones = Nearly equal in width and length (wrist and feet bones, trapezoid)
3. Flat bones = Thin and composed of two parallel plates of compact bone encasing spongy bone (cranial bones, sternum).
4. Irregular bones = Complex shapes, do not fit in other categories (vertebrae).
5. Sesamoid bones = Develop in tendons due to wear and tear (patella).

Question 3

Describe the 4 bone cell types

Answer 3

1. Osteoprogenitors = Unspecialized bone stem cells. Mature into osteoblasts. Found in inner portion of periosteum (membrane that wraps bone), endosteum (membrane of inside of bone) and canals containing blood vessels in bone.
2. Osteoblasts = Bone building cells. Function to build bone extracellular matrix and initiate calcification. Eventually mature into osteocytes. Found in extracellular matrix.
3. Osteocytes = Mature bone cells. Maintain daily metabolism (exchange of waste and nutrients with blood). Found in lacunae.
4. Osteoclasts = Huge cells made up of fusion of monocytes. Function to break down bone extracellular matrix through reabsorption. Found on bone surfaces undergoing reabsorption.

Question 4

Spongy bones function and location

Answer 4

Function = Weight reduction, shock absorption and houses red and yellow bone marrow.
Location = Interior of short, flat and sesamoid bones (sternum).

Question 5

Compact bones function and location

Answer 5

Function = Support, strength and protection.
Location = Encases spongy bone and is the bulk of long bones (Femur shaft).

Question 6

Compact bone structure

Answer 6

• A regular structure of repeating osteons surrounding central canals of blood vessels and nerves.
• Osteons contain concentrically arranged lamellae containing an extracellular matrix.
• Between lamellae are small spaces called lacunae, which contain osteocytes.
• These lacunae are surrounded by small channels called canaliculi, which contain extracellular fluid and the slender processes of osteocytes.
  Results in an interconnected system.

Question 7

Spongy bone structure

Answer 7

• Does not contain osteons.
• An irregular structure of lamellae containing an extracellular matrix is arranged in a pattern of thin columns called trabeculae.
• Each trabecula contains concentric lamellae which have small spaces between them called lacunae where osteocytes reside.
• The lacunae are surrounded by small channels called canaliculi which contain extracellular fluid and slender processes of osteocytes.
• Results in an interconnected system.

Question 8

What is Osteoporosis

Answer 8

• A condition of porous bones.
• Occurs when bone resorption (breakdown) outpaces bone deposition (formation.
• Therefore osteoclasts are outpacing osteoblasts.