UNIT SIX: BONE AND SKELETAL TISSUE

Question 1

COMPARE AND CONTRAST THE STRUCTURE OF THE FOUR CLASSES OF BONE AND PROVIDE AN EXAMPLE OF EACH

Answer 1

→ long: are longer in comparison to width, they serve as an appendage and lever for muscle contraction and movement. Ex. femur
→ short: small square shaped bones that are mainly used for stability and minor movement. Ex. tarsals of the feet.
Sesamoid: are sesame shaped bones that are only found in tendons, they help resist compression, the only sesamoid bone we all share is the patella.
→ flat: are flat curved bones that serve as an attachment site for muscles. They also create the most bone marrow. Ex. coxal bone
→ irregular: are too weirdly shaped to fit any other of the above categories. Ex. skull.

Question 2

NAME THE SEVEN FUNCTIONS OF BONE

Answer 2

→ movement: bone acts as an appendage or lever for muscle contraction
→ support: bone supports the body against gravity
→ protection: protects the brain, spinal cord, and other internal organs
→ mineral and growth factor storage: stores calcium and growth factor in trabeculae of spongy bone.
→ triglyceride (fat) storage: stored in yellow bone marrow in medullary cavity
→ red blood cell production: produced in the red bone marrow of spongy bone
→ hormone production: osteocalcin produced by bone regulates blood glucose, metabolism and insulin.

Question 3

GROSS ANATOMY OF LONG AND FLAT BONES

Answer 3

→ epiphysis: are the distal and proximal ends of the bone
→ diaphysis: the middle long part of a long bone
→ articular cartilage: hyaline cartilage on the ends of bone to reduce friction and provide a smooth surface.
→ red bone marrow: located in spongy bone and produced red blood cells.
→ medullary cavity: the central hollow canal within a bone.
→ endosteum: lines the inside of the medullary cavity.
→ yellow bone marrow: where fat is stored, is only present in adults.
→ periosteum: lines the outside of the bone, has a fibrous layer containing fibrous material and an osteogenic layer that contains stem cells.
→ nutrient artery: vascularizes the bone
→ epiphyseal line: is the remnants of the epiphyseal plate that’s made up of hyaline cartilage and promotes longitudinal bone growth in kids. At a certain age it will become ossified.

Flat bone anatomy is 2 layers of compact bone with lined periosteum encasing a layer of spongy bone.

Question 4

HISTOLOGY OF COMPACT BONE + DIFFERENCES BETWEEN COMPACT AND SPONGY BONE

Answer 4

The singular structural unit of bone is called an osteon. It contains a central canal containing blood vessels and nerves. These vessels can travel throughout the osteon in right angle canals called perforating canals. Surrounding the central canal are ring-like structures of compact bone called lamellae. The outskirts of lamellae contain lacunae that contain osteocytes. The lacunae can communicate with one another using canaliculi.

Spongy bone and compact bone are different in these ways, compact bone is dense and hard and is made up of collagen and osteons. Spongy bone does not have osteons and instead has trabeculae that contains calcium phosphate crystals and growth factor. Spongy bone also has collagen, as well as yellow and red bone marrow.

Question 5

CHEMICAL COMPOSITION OF BONE

Answer 5

Bone contains inorganic and organic substances within it. The organic substances include the collagen fibers that make up the bone and give bone its strength. Organic substances also include the osteocytes, osteoblasts, etc. the inorganic contents include the calcium phosphate crystals found in the trabeculae of spongy bone, this gives bone its hardness.

Question 6

EXPLAIN INTRAMEMBRANOUS OSSIFICATION AND ENDOCHONDRAL OSSIFICATION

Answer 6

→ intramembranous ossification: bone that comes from a fibrous membrane, ex. Clavicle and skull
→ endochondral ossification: comes from the replacement of hyaline cartilage into bone, ex, epiphyseal plate.

Question 7

DESCRIBE POSTNATAL GROWTH AND THE HORMONES THAT AFFECT IT.

Answer 7

→ the epiphyseal plate will continue to grow longitudinally because of the release of growth hormone (regulated by thyroid). This typically stops at adolescents. Bones will also grow appositionally (cartilage making it thicker). Estrogen and testosterone facilitate growth spurts in kids. Growth usually stops (longitudinally) during adolescence. However some facial bones may continue to grow.

Question 8

DESCRIBE ROLES OF GRAVITATIONAL AND MECHANICAL FORCES IN BONE REMODELLING

Answer 8

The less forces and stresses that are put onto bone, the weaker they will get, this is Wolf’s law. If you don’t use a bone, osteoclasts will break down and eat the bone and use the resources in other areas. However if you always use these bones, the osteoclasts will be inhibited and your bones will continue to grow stronger.

Question 9

EXPLAIN HOW BONE REMODELING AND CALCIUM ARE INVOLVED IN CALCIUM HOMEOSTASIS.

Answer 9

PTH will stimulate osteoclasts to break down bone, releasing calcium into the bloodstream when there are low amounts. If calcium levels are high then PTH will not be released and thus osteoclasts are not stimulated. This causes bone deposit where calcium is brought back into the bones. Bone resorption is the breaking down of the bone.

Question 10

LIST THE 4 STAGES OF BONE REMODELLING

Answer 10

→ hematoma formation
→ fibrocartilaginous formation
→ bony callus formation
→ bone remodeling