2-14-19 test

Question 1

How does compact (dense) bone differ from cancellous (spongy) bone

Answer 1

Compact bone: tissue that is dense, hard, and forms the protective exterior portion of all bones; has bone cells embedded in extracellular matrix that is primarily collagen and inorganic salts; resists compressional forces
Cancellous bone: tissue inside compact bone which is very porous (full of tiny holes); has bone cells embedded in mineral salts and collagen fibers; has trabeculae (branching, bony plates with irregular spaces between them); is on the ends (and insides) of long bones; is strong and light; is subject to compressional forces

Question 2

What is osteology?

Answer 2

The study of bones

Question 3

What is an osteocyte?

Answer 3

Mature bone cell encased within bony extracellular matrix

Question 4

What is osteoclast?

Answer 4

Cell which resorbs (breaks down or cuts up) bone

Question 5

Describe and locate the microscopic structures of compact bone:

Answer 5

Osteocytes are located in tiny, bony chambers called lacunae
Osteocytes can communicate with one another through tiny channels known as caniliculi
Osteocytes and layers of extracellular materials are clustered around a central canal (housing blood vessels and nerves) to form a cylinder-shaped unit called the osteon
Each osteon (also called a Haversian system) is the structural and functional unit of compact bone
Many osteons cemented together form compact bone

Question 6

How does the microscopic structure of spongy bone differ from that of compact bone?

Answer 6

Spongy bone doesn’t have central canals around which bone cells aggregate; instead, cells lie within bony ridges called trabeculae and get nutrients from substances diffusing through canaliculi that lead to the surface of the trabeculae

Question 7

Which of the four major tissue types (epithelial, connective muscular, or nervous) are found in the bone?

Answer 7

Primarily connective and nervous; connective (dense fibrous connective- tendons; supportive connective- bone and cartilage; fluid connective-blood) nervous (nerve fibers)

Question 8

When do bones first begin to form?

Answer 8

The first 2wks of prenatal development

Question 9

How do intramembranous bones differ from endochondral bones?

Answer 9

Intramembranous bones: are mostly broad, flat bones like the skull bones
Endochondral bones: include most of the bones of the skeleton

Question 10

How does the origin of intramembranous bones differ from endochondral bones?

Answer 10

Intramembranous bones: originate within sheet-like layers of connective tissue
Endochondral bones: begin as masses of hyaline cartilage that act as a model upon which bone is later formed

Question 11

What are the first steps involved in long bone development?

Answer 11

1. Hyaline cartilage acts as a model for long bone development that stars during the first weeks of prenatal development
2. Hyaline cartilage tissue breaks down and the periosteum (with osteoblasts and blood vessels) develops
3. Osteoblasts first form spongy bone in the primary ossification center (space previously occupied by the cartilage). Osteoblasts next deposit a thin layer of compact bone around the spongy bone. This will eventually become the diaphysis
4. Developing bone thickens as compact bone is deposited on the outside
5. As compact bone forms on the outside, osteoclasts erode tissue on the inside creating the medullary cavity
6. The epiphysis remain cartilaginous and grow. Secondary ossification center appear in the epiphyses and spongy bone forms in all directions from them
7. A band of cartilage known as the epiphyseal plate remains between the primary ossification centers of the diaphysis and the secondary ossification centers of the epiphyses

Question 12

How does the long bone increase in length?When does it stop lengthening?

Answer 12

1. Growth at the epiphyseal plate causes the bone to grow in length
2. Actively dividing cartilage cells lay down layer upon layer of new cartilage cells which extend out from the epiphyseal plate
3. The cartilage cells becomes calcified
4. Osteoclasts break down the calcified matrix
   osteoblasts deposit bone tissue in place of the calcified cartilage
5. A long bone continues to lengthen as long as the cartilaginous cells of the epiphyseal plate are active
6. Once the ossification centers of the diaphysis and epiphysis meet and the epiphyseal plates ossify, lengthening stops. The epiphyseal plates of children are very well defined, while those of adults whose bone growth has ceased are indistinct

Question 13

What is meant by the phrase “homeostasis of bone tissue”?

Answer 13

Resorption and deposition are regulated so the total mass of bone tissue within an adult skeleton remains relatively constant throughout life

Question 14

What organ system regulates bone resorption and deposition?

Answer 14

The endocrine system. Resorption occurs when parathyroid hormone stimulates osteoclasts to break down bone. Deposition occurs when calcitonin hormone from the thyroid gland stimulates osteoblasts to form bone. A negative feedback system is involved

Question 15

What factors affect bone growth, development, and repair? Explain

Answer 15

Nutrition and exposure to sunlight
Vitamin d is needed for proper calcium absorption. It can be synthesized from precursor molecules when your skin is exposed to sunlight. A deficiency leads to rickets in children (bowling of long bones) and osteomalacia in adults (softening and deformity of bone)

Question 16

Hormonal secretions

Answer 16

An excess of growth hormone before the epiphyseal plates ossify leads to pituitary gigantism and even bone deformities

Question 17

Physical exercise

Answer 17

Physical stress (exercise) stimulates bone growth

Question 18

genetics

Answer 18

Ectrodactyly is a genetic disorder resulting in abnormal development of the fingers and toes (lobster claw syndrome)

Question 19

fractures

Answer 19

Bone fractures can be classified according to cause and nature of the break

Question 20

Cause

Answer 20

Traumatic fracture- due to injury

Spontaneous or pathological fracture- due to disease

Question 21

Nature of the break

Answer 21

Complete or compous (open fracture)- exposed to outside by an opening in the skin
Incomplete or closed fracture-protected by uninjured skin

Question 22

What are the two types of incomplete fractures?

Answer 22

Greenstick: breaks occurs in the convex surface of the bend in the bone
Fissured: longitudinal break

Question 23

What are the four types of complete fractures?

Answer 23

Comminuted: fragments the bone
Transverse: break occurs at a right angle to the axis of the bone
Oblique: occurs at the angle other than a right angle to the axis of the bone
spiral : caused by twisting a bone excessively

Question 24

Describe the steps involved in healing a fracture

Answer 24

1. Escaping blood from vessels forms a hematoma
2. New blood vessels begin to develop. Spongy bone forms close to them and fibrocartilage forms farther away from the blood vessels
3. A bony callus replaces the fibrocartilage
4. Osteoclasts remove the excess bony tissue, restoring the bone to its former likeness

Question 25

What is hematopoiesis?

Answer 25

The formation of blood cells: red, white and platelets. It takes place in red bone marrow (found in most infant bones) and in the spongy bone of skull, ribs, sternum, clavicles, vertebrae, and hipbones)

Question 26

Name some life span changes that occur in the skeletal system as the body ages

Answer 26

Decrease in height at about age 30
Calcium levels falls
Bones become brittle
Osteocytes outnumber osteoblasts 
Spongy bone weakens before compact bone
Bone loss rapid in menopausal women 
Hip fractures common
Vertebral compression fractures common

Question 27

Tarsal bones

Answer 27

(superior, then clockwise on right foot)

talus , calcaneus, navicular, medial cuneiform, intermediate cuneiform, lateral cuneiform cuboid

Question 28

Carpal bones

Answer 28

(proximal row, then distal row)

scaphoid , lunate, triquetrum, pisiform, trapezium, trapezoid, cuboid, hamate