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PJ1311 YEAR 1 (THE HUMAN BODY) > the physiology of the bone > Flashcards

the physiology of the bone Flashcards

1
Q

osteocytes

A

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

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2
Q

osteoblasts

A

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.

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3
Q

osteoclasts

A

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.

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4
Q

ossification

A

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.

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5
Q

state some functions of the skeleton

A

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

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6
Q

briefly describe how the skeletob protects the body against acidosis

A

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.

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7
Q

the three main components of the bone

A

cortical bone(compact bone)

trabecular bone(cancellous/spongy bone)

bone marrow cavity

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8
Q

name some properties of the cortical and trabecular bone respectively

A

Strong, dense, regular structure

Lightweight, irregular lattice, porous/permeable

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9
Q

lamellar bone

A

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

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10
Q
A
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10
Q

a brief description of the harvesian systems

A

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.

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11
Q

some functions of harvesian systems

A

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

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12
Q

does the bone have a fixed or static structure

A

no

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13
Q

the main or primary mineral of the bone is?

A

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

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13
Q

what percentage of the bone is;
organic
minerals

A

30% organic
70% minerals

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14
Q

osteoblasts are derived from?

A

mesenchym stem cell line

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15
Q

main functions of osteoblasts

A

bone formation

mineralisation of the matrix

secretion of proteinous organic matrix

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16
Q

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

A

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.

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17
Q

factor secreted by the osteoblasts to activate osteoclasts

A

RANK- Ligand

aka (Receptor Activator of Nuclear Factor κB Ligand)

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18
Q

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

A

PTH
Vitamin D
Oestrogen

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19
Q

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 ?

A

they differentiate into osteocytes

they differentiate into lining cells

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

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20
Q

osteoclasts are derived from?

A

hematopoietic stem cells

21
Q

precurser cells of osteoclasts

A

macrophages or monocytes

22
Q

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

A

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

23
Q

bone resorption is mediated by which type of bone cells

A

osteoclasts

24
Q

purposes of bone resorption

A

Radial growth
Bone remodelling Maintaining vascularity
Liberating ions

25
Q

osteogenesis

A

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

26
Q

the two main mechanisms of bone ossification

A

endochondral ossification and intramembranous ossification

27
Q

intramembranous ossfication

A

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

28
Q

endochondral ossification

A

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

29
Q

the two main requirements for osteogenesis to occur

A

matrix formation

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

30
Q

what causes the following;
growth in length of a bone

growth in diameter of a bone

A

by proliferation of chondrocytes at the epiphyseal plates and at the primary ossification front

deposition of new bone under the periosteal collar

31
Q

calcium functions in bone

A

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.

32
Q

phosphorus function in bone

A

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

33
Q

primary phosphate regulation occurs in which organ

A

the kidneys

34
Q

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

A

it decreases phosphate levels as PTH enhances phosphate secretion

35
Q

it is a vitamin as well

which hormone decreases PTH production

A

vitamin D

inhibition of PTH production means an increase in phosphate levels

36
Q

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

A

vitamin d and PTH

they both increase calcium levels in the body

37
Q

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

A

3
activation of osteoclasts

Enhancement of Renal Calcium Reabsorption

stimulation of vitamin D activation

38
Q

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

state them

A

2

Renal Reabsorption
Intestinal Absorption

39
Q

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

A

false

40
Q

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

A

true

41
Q

osteoclasts express PTH receptors on their surfaces, true or false

A

false, they do not

42
Q

prolonged PTH receptor activation causes?

A

bone resorption

43
Q

intermittant= irregular

intermittant PTH receptor activation causes?

A

bone formation

44
Q

hypercalcaemia and hyperphospataemia increase vitamin D activity, true or false

A

no they decrease it
hypocalcaemia and…. increase it rather

45
Q

name the enzymes involved in vitamin D synthesis and their functions

A

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.

46
Q

transcalciferin function in vitamin d synthesis

A

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.

47
Q

what are some actions (functions ) of vitamin D

A

increase absorption of Ca2+

Indirectly stimulate osteoclast activity (as PTH)

Inhibit PTH synthesis (feedback inhibition)

48
Q

difference between osteomalacia and rickets

A

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

both affect the bone’s mineralisation process, thereby causing soft and weak bones

49
Q
A
50
Q

respectively name some disorders of;

bone mineralisation

bone density

A

osteomalacia
rickets
Hypophosphatasia

osteoporosis
Paget’s disease of bone
Osteopenia

51
Q

name some risk factors of osteoporosis

A

Age
Smoking
Sex
Alcohol
Ethnicity
Exercise
Familial
Diet

52
Q

what disease is considered a precursor to osteoporosis

A

osteopenia

PJ1311 YEAR 1 (THE HUMAN BODY) (34 decks)

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