Skeletal System

Question 1

List the functions of the skeletal system with a short description

Answer 1

1. Support (bones support the soft tissues and provide attachment sites for muscles, making them a structural framework for the body)
2. Protection (internal organs are protected by the bones)
3. Assist in movement (assis skeletal muscles)
4. Mineral homoestasis (bones store and release several minerals like calcium and phosphorus)
5. Production of blood cells (homeopoiesis occurs in red bone marrow)
6. Triglyceride storage (yellow bone marrow in adult bones)

Question 2

What are the types of bone shape?

Answer 2

Long bones, short bones, flat bones and irregular bones

Question 3

Describe long bones and give examples

Answer 3

They consist of a shaft with two ends, like the femus, the humerus, the phalanges

Question 4

Describe short bones and give examples

Answer 4

They are cube like and exist in wrists (carpals) and ankles (tarsals)

Question 5

Describe flat bones and give examples

Answer 5

they are thin and usually curved, like skull bones and ribs

Question 6

Describe irregular bones and give examples

Answer 6

They do not fit in any other category like vertebrae or hip bones

Question 7

What are the various parts of a long bone?

Answer 7

The diaphysis, the epiphyses, the metaphyses, the hyaline cartilage, the periosteum, the endosteum, the marrow cavity, the red marrow, the yellow marrow

Question 8

What is the diaphysis?

Answer 8

The shaft of the long bone

Question 9

What are the epiphysis?

Answer 9

The ends of the bone

Question 10

What are the metaphyses?

Answer 10

The areas between the epiphysis and the diaphysis that include the epiphyseal plates in growing bones

Question 11

What is hyaline cartilage and where is it located?

Answer 11

Flexible gel-like cartilage at the ends of long bones to protect from shocks

Question 12

What is the periosteum and what is its use?

Answer 12

A connective tissue that covers the surface of the bones. It contains osteogenic cells, it protects bones, assists in fracture repair, helps nourish bone tissue and serves as attachment point for ligaments and tendons

Question 13

What is the marrow cavity?

Answer 13

The space within the diaphysis

Question 14

What is red marrow and where is it located?

Answer 14

The site of homoepoesis, in the epiphyses and metaphyses

Question 15

What is yellow marrow and where is it located?

Answer 15

The site of triglyceride storage and in the diaphysis

Question 16

What is the endosteum?

Answer 16

The lining of medullary cavity

Question 17

What are the principal bone cells and their function?

Answer 17

osteoprogenitor (osteogenic cells, stem cells that differentiate into osteoblasts), osteoblasts (bone building cells that produce matrix), osteocytes (mature bone cells), osteoclasts (break down bone tissue)

Question 18

What is bone matrix made of ?

Answer 18

inorganic salts like hydroxyapatite and calcium carbonate, and collagen fibers.

Question 19

What is the process of calcification?

Answer 19

When the inorganic salts are deposited in the framework of collagen fibers.

Question 20

What is the use of minerals in the bone matrix, and what is the use of collagen?

Answer 20

The salts confer the hardness, and the collagen the tensile strength

Question 21

What is the unit of compact bone ?

Answer 21

Osteons, or harvesian systems

Question 22

What are the components of osteons?

Answer 22

blood vessels, lymphatic vessels, nerves, osteocytes in the calcified matrix

Question 23

What is cancellous bone made of ?

Answer 23

traberculae and red bone marrow

Question 24

What are traberculae?

Answer 24

columns or beams of bones in the spongy bones

Question 25

Where is spongy bone found? What is its use?

Answer 25

In most of the structure of short, flat and irregular bones, and in the epiphyses of long bones. It's light, and supports and protects the bone marrow.

Question 26

What is ossification, or osteogenesis?

Answer 26

The process of bone growing

Question 27

What are the two types of ossification?

Answer 27

Intramembraneous ossification and endochondral ossification

Question 28

What is the general definition of intramembraneous ossification, and which bones does it produce?

Answer 28

It is when the formation of bone occurs directly from mesenchymal cells (undifferentiated connective tissue cells), and it makes the skull and mandibles

Question 29

What is the general definition of endochondral ossification and what bones does it produce?

Answer 29

It is when the bones form from hyaline cartilage, and it produces most bones in the body

Question 30

Desribe the steps involed in intramembraneous ossification

Answer 30

1. Mesemchymal cells differentiate into osteoblasts, which cluster together, creating the center of ossification. 2. The osteoblasts generate osteoids, the uncalcified matrix. 3. The matrix gets calcified, which traps osteoblasts, turning them into osteocytes. 4. These organize into trabercular, forming structures around blood vessels forming spongy bones 5. The mesenchymal cells outside form periosteum , which them forms an inner layer of osteoblasts, which will produce compact bone around the spongy bone. The blood vessels become red marrow.

Question 31

Describe the steps involved in endochondral ossification

Answer 31

1. Mesenchymal cells differentiate into chondroblasts, which makes chondrocytes, which makes a cartilage scaffold with a perichondrium layer, in the shape of the bone. 2. The middle chondrocytes swell, and it starts calcifying the matrix. The end parts of the matrix are not calcified. 3. The middle part of the shaft becomes vascularized, which changes the perichodrium to the periosteum. The calcified matrix prevents nourishement of the chondrocytes , and lead to chrondocyte death. 4. Vascularization reaches the dead cells, creating the primary center of ossification. There is a mix of calcified cartilage and calcified bone from the the osteoblasts form the periosteum. 5. The osteoclasts destroy the center cavity to create the medullary cavity and the osteoblasts create bone around it (osteoids, which become calcified, and create traberculae, then compact bone) 6. Secondary ossification centers form in the epiphyses.

Question 32

Explain longitudinal bone growth

Answer 32

It is a type of endochondrial ossification. The epiphyseal growth plate changes into bone, until it becomes the epiphyseal line, which indicates the bone has stopped growing.

Question 33

Explain diameter growth in bone

Answer 33

It is intramembraneous growth from the periosteum by making osteoblasts while the osteoclasts resorb bones in the endosteum in the spongy bone.

Question 34

What is remodeling?

Answer 34

The fact that bone constantly breaks down broken or unused bones with osteoclasts, and rebuilds it with osteblasts.

Question 35

What are the minerals needed for bone growth?

Answer 35

Calcium, magnesium and phosphorus

Question 36

What are the vitamins needed in bone growth?

Answer 36

Vitamin A, B12, C, D and K

Question 37

What are the the important hormones for bone growth during childhood?

Answer 37

insulin-like growth factors, stimulated by the human growth hormone

Question 38

What hormones are necessary for bone growth in general?

Answer 38

Thyroid hormones, insulin and calcitonin

Question 39

What hormones stimulate sudden growth during puberty?

Answer 39

estrogen and testosterone

Question 40

What is osteoporosis?

Answer 40

A disease due to aging where the bone resorption is greater than bone formation, which results in weakening of the bones.

Question 41

What systems need a balanced calcium level?

Answer 41

Skeletal cardiac, nervous.

Question 42

What calcium level do we need?

Answer 42

10mg/L

Question 43

What happens when there is an increase in calcium levels?

Answer 43

1. The thyroid gland releases calcitonin 2. Osteoclasts activity is inhibited 3. Calcium reabsorption in the kidneys is decreased 4. The calcium level in the blood decreases

Question 44

What happens when calcium levels decrease?

Answer 44

1. The receptors in the parathyroid gland release parathyroid hormones (PTH) 2. It stimulates osteoclasts to release more calcium 3. It stimulates the kidneys to reabsorb more calcium 4. Calcium is absorbed from the intestines through vitamin D synthesis 5. Calcium in the blood increases.

Question 45

What are thw two divisions of the skeletal system and what do they comprise?

Answer 45

axial (skull, thoracic cage and vertebral column) and perpendicular (all other bones)

Question 46

What are the main bones in the skull?

Answer 46

cranial portion and facial portion

Question 47

What are the main bones in the pectoral girdle?

Answer 47

clavicle, scapula

Question 48

What are the main bones in the thoracic cage?

Answer 48

sternum, ribs

Question 49

What are the main bones in the upper limb?

Answer 49

humerus, radius, ulna, carpals, metacarpals, phalanges

Question 50

What are the main bones in the lower limb?

Answer 50

femus, patella, tibia, fibula, tarsals, metatarsals, phalanges

Question 51

What are the main bones in the pelvic girdle?

Answer 51

hip bones

Question 52

Describe the structure of an osteon

Answer 52

Osteons are made of concentric lamellae, that have various orientations of collagen fibers to resist torsion. In the middle, the haversian canal contain blood vessels, nerves and lymphatic vessels. In between the lamellae in the bone matrix are small spaces called lacunae, in which we find trapped osteocytes. The osteocytes recieve nutrients through small canals in between lacunae called canaliculi.