the physiology of the bone

Question 1

osteocytes

Answer 1

Osteocytes are mature bone cells derived from osteoblasts. .

They are embedded within the bone matrix and are responsible for maintaining bone tissue by regulating mineral homeostasis and responding to mechanical stress

Question 2

osteoblasts

Answer 2

Osteoblasts are bone-forming cells responsible for synthesizing and depositing new bone tissue during bone formation and repair

They secrete collagen and other proteins that form the organic matrix of bone, which is then mineralized to create new bone tissue.

Question 3

osteoclasts

Answer 3

Osteoclasts are large multinucleated cells responsible for bone resorption, which is the process of breaking down bone tissue

They play a crucial role in bone remodeling and repair by removing old or damaged bone tissue.

Question 4

ossification

Answer 4

Ossification is the process by which bone tissue is formed, involving the deposition of mineralized matrix by osteoblasts and subsequent remodeling of this matrix into mature bone tissue.

Question 5

state some functions of the skeleton

Answer 5

Structural support for heart, lungs and marrow

Protection for brain, uterus and other internal organs

Attachment sites for muscles allowing limb movement

Mineral reservoir for calcium and phosphorus

Defence against acidosis

Trap for some dangerous minerals such as lead

Question 6

briefly describe how the skeletob protects the body against acidosis

Answer 6

The skeleton helps regulate pH by acting as a buffer, absorbing excess acid and releasing alkaline compounds, thereby maintaining the body’s acid-base balance.

Question 7

the three main components of the bone

Answer 7

cortical bone(compact bone)

trabecular bone(cancellous/spongy bone)

bone marrow cavity

Question 8

name some properties of the cortical and trabecular bone respectively

Answer 8

Strong, dense, regular structure

Lightweight, irregular lattice, porous/permeable

Question 9

lamellar bone

Answer 9

a type of bone tissue characterized by its organized arrangement of collagen fibers into layers or lamellae. These layers provide strength and resilience to bone.

note that it is a component of both the cortical and trabecular bones

Question 10

a brief description of the harvesian systems

Answer 10

cylindrical units found primarily in compact bone. Each Haversian system comprises concentric layers of lamellar bone encircling a central canal housing blood vessels and nerves.

Question 11

some functions of harvesian systems

Answer 11

play a pivotal role in bone remodeling and repair processes.

They facilitate the exchange of nutrients and waste products, contributing to bone metabolism and homeostasis.

provides structural support to the bone

Question 12

does the bone have a fixed or static structure

Answer 12

no

Question 13

the main or primary mineral of the bone is?

Answer 13

hydroxyapatite
(Ca10(PO4)6(OH)2)

Question 13

what percentage of the bone is;
organic
minerals

Answer 13

30% organic
70% minerals

Question 14

osteoblasts are derived from?

Answer 14

mesenchym stem cell line

Question 15

main functions of osteoblasts

Answer 15

bone formation

mineralisation of the matrix

secretion of proteinous organic matrix

Question 16

osteoblasts are low in mitochondria and golgi content, true or false

Answer 16

false, they are high in mitochondria and golgi content

to provide energy in the form of ATP (adenosine triphosphate) to support the metabolic processes required for osteoblast activity, including the synthesis and secretion of the organic components of the bone matrix, such as collagen.

Question 17

factor secreted by the osteoblasts to activate osteoclasts

Answer 17

RANK- Ligand

aka (Receptor Activator of Nuclear Factor κB Ligand)

Question 18

osteoblasts possess some hormone receptors. Name three of the hormones for which they have these receptors?

Answer 18

PTH
Vitamin D
Oestrogen

Question 19

what happens to osteoblasts in each of these contexts respectively…

when trapped by a new bone?

when they remain on the surface of a new bone ?

Answer 19

they differentiate into osteocytes

they differentiate into lining cells

note that the cells that do not undergo any of these processes undergo apoptosis

Question 20

osteoclasts are derived from?

Answer 20

hematopoietic stem cells

Question 21

precurser cells of osteoclasts

Answer 21

macrophages or monocytes

Question 22

osteoclasts are formed on fusion of it’s precursor cells. which factors on the precursor cells stimulate this fusion?

Answer 22

RANK receptors on the precursor cells stimulate the fusion of the precursor cells

Question 23

bone resorption is mediated by which type of bone cells

Answer 23

osteoclasts

Question 24

purposes of bone resorption

Answer 24

Radial growth Bone remodelling Maintaining vascularity Liberating ions

Question 25

osteogenesis

Answer 25

Process whereby calcium phosphate crystals precipitate and attach to a collagenous lattice support

Question 26

the two main mechanisms of bone ossification

Answer 26

endochondral ossification and intramembranous ossification

Question 27

intramembranous ossfication

Answer 27

bone formation that primarily occurs in long bones like the femur, and involves the replacement of cartillage with bone tissue

Question 28

endochondral ossification

Answer 28

bone formation that primarily occurs in flat and some irregularly shaped bones. it involved the differentiation of mesenchymal cells (embryonic connective tissue cells) into osteoblasts within a fibrous membrane

Question 29

the two main requirements for osteogenesis to occur

Answer 29

matrix formation mineralisation (involves the deposition of calcium phosphate crystals onto the collagen fibers within the organic matrix)

Question 30

what causes the following; growth in length of a bone growth in diameter of a bone

Answer 30

by proliferation of chondrocytes at the epiphyseal plates and at the primary ossification front deposition of new bone under the periosteal collar

Question 31

calcium functions in bone

Answer 31

play a crucial role in bone mineralization, providing strength and rigidity to the bone structure. They also participate in various cellular signaling processes within bone cells.

Question 32

phosphorus function in bone

Answer 32

combine with calcium ions to form hydroxyapatite crystals, the primary mineral component of bone.

Question 33

primary phosphate regulation occurs in which organ

Answer 33

the kidneys

Question 34

what influence does an increase in PTH have on phosphate levels in the blood

Answer 34

it decreases phosphate levels as PTH enhances phosphate secretion

Question 35

# it is a vitamin as well which hormone decreases PTH production

Answer 35

vitamin D ## Footnote inhibition of PTH production means an increase in phosphate levels

Question 36

two main hormones that regulate calcium levels and their effects on calcium in the body

Answer 36

vitamin d and PTH they both increase calcium levels in the body

Question 37

how many mechanisms does PTH use to regulate calcium levels in body state these mechanisms

Answer 37

3 activation of osteoclasts Enhancement of Renal Calcium Reabsorption stimulation of vitamin D activation

Question 38

how many main mechanisms does vitamin D use to regulate calcium levels in the body state them

Answer 38

2 Renal Reabsorption Intestinal Absorption

Question 39

PTH does not increase phosphate excretion in urine, true or false

Answer 39

false

Question 40

an increase in vitamin d increases calcium and phosphate absorption from the intestine, true or false

Answer 40

true

Question 41

osteoclasts express PTH receptors on their surfaces, true or false

Answer 41

false, they do not

Question 42

prolonged PTH receptor activation causes?

Answer 42

bone resorption

Question 43

# intermittant= irregular intermittant PTH receptor activation causes?

Answer 43

bone formation

Question 44

hypercalcaemia and hyperphospataemia increase vitamin D activity, true or false

Answer 44

no they decrease it hypocalcaemia and.... increase it rather

Question 45

name the enzymes involved in vitamin D synthesis and their functions

Answer 45

7-dehydrocholesterol reductase: Converts 7-dehydrocholesterol to cholesterol in the skin upon exposure to UVB radiation. 25-hydroxylase: Converts vitamin D into its active form, calcitriol, in the liver. 1-alpha-hydroxylase: Converts calcidiol to calcitriol in the kidneys, the active form of vitamin D. 24-hydroxylase: Converts calcitriol into its inactive form, calcitroic acid, for regulation of vitamin D levels.

Question 46

transcalciferin function in vitamin d synthesis

Answer 46

Its main role is to transport vitamin D from where it is synthesized (skin or obtained from diet) to target tissues where it is needed for various physiological processes.

Question 47

what are some actions (functions ) of vitamin D

Answer 47

increase absorption of Ca2+ Indirectly stimulate osteoclast activity (as PTH) Inhibit PTH synthesis (feedback inhibition)

Question 48

difference between osteomalacia and rickets

Answer 48

Softening of bones in adults due to vitamin D deficiency or metabolic issues while Rickets is a similar condition occurring in children during growth periods, leading to bone deformities ## Footnote both affect the bone's mineralisation process, thereby causing soft and weak bones

Question 50

respectively name some disorders of; bone mineralisation bone density

Answer 50

osteomalacia rickets Hypophosphatasia osteoporosis Paget's disease of bone Osteopenia

Question 51

name some risk factors of osteoporosis

Answer 51

Age Smoking Sex Alcohol Ethnicity Exercise Familial Diet

Question 52

what disease is considered a precursor to osteoporosis

Answer 52

osteopenia