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Medicine 2 Week 6 - 11 > Bones 1 & 2 > Flashcards

Bones 1 & 2 Flashcards

1
Q

What type of tissue is cartilage and what is its function

A

Specialised connective tissue with a support function (e.g. shock absorbing or tough/flexible)

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2
Q

What type of cells are in cartilage

A

Chondrocytes

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3
Q

What makes up the matrix of cartilage (general)

A

Type II collagen
Elastin
Proteoglycans (GAGs)
Others depending on type

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4
Q

Chondroblast

A

Immature chondrocytes

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5
Q

Vaguely describe the development of chondrocytes

A

Derived from embryonic mesenchyme (spindle) that turn into rounder clusters of chondroblasts surrounded by a layer of perichondrium (mesenchyme derived fibroblastic cells & collagen)

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6
Q

Interstitial Growth

A

Cell division resulting in the growth of a tissue type

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7
Q

Appositional Growth

A

Growth by forming new layers on the surface of pre-existing layers

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8
Q

Does cartilage grow by interstitial or appositional growth and how

A

Both

Interstitial - Limited division of chondroblasts in ECM

Appositional - New chondroblasts from perichondrium

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9
Q

Lacuna of cartilage

A

The cavities in the matrix that chondrocytes are contained in

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10
Q

What percentage of cartilage ECM is water

A

70%

**DONT REMEMBER

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11
Q

Composition of proteoglycans

A

GAGs attached to a core protein

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12
Q

Role of proteoglycan aggreggates

A

Providing compressive strength as a flexible cushioned surface in collagen

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13
Q

Types of Cartilage

A

Hyaline Cartilage
Elastic Cartilage
Fibrocartilage

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14
Q

Composition of Hyaline Cartilage

non ground substance

A

Type II collagen only

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15
Q

Broad location of hyaline cartilage

A

Smooth glistening (glassy) articular surfaces - Articular ends of long bones, Ventral rib cartilage, tracheal rings

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16
Q

Composition of Elastic Cartilage

non-ground substance

A

Type II Collagen + Elastin

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17
Q

Broad location of Elastic Cartilage

non-ground substance

A

End of nose, Ears, Larynx

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18
Q

Composition of Fibrocartilage

A

Type II & Type I collagen -strong

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19
Q

Broad location of Fibrocartilage

A

Intervertebral disks, Insertions of ligaments & tendons, Joint capsules, Sternoclavicular joint

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20
Q

What type of cartilage is the epiglottis

A

Elastic Cartilage

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21
Q

Hyaline cartilage at joints

A

Resists compression due to elasticity & stiffness of proteoglycans

Tensile strength due to collagen & hydrogel ground substance

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22
Q

Describe vascularity of cartilage and consequence

A

Most is avascular, limiting repair & regeneration when damaged

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23
Q

Presence of perichondrium at articular surfaces of joints and why

A

No perichondrium so no source of new chondroblasts

This would introduce friction otherwise

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24
Q

Reversibility of cartilage atrophy

A

Reversible but time consuming

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25
Q

What type of tissue is bone

A

Specialised connective tissue

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26
Q

What ions does bone act as a reservoir for

A

Calcium & Phosphate

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27
Q

Composition of bone

A

Cell & extracellular matrix

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28
Q

Where does haematopoiesis occur

A

Bone marrow

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29
Q

Energy need of bone (vaguely) and why

A

High

It is constantly adapting, remodelling and also performing roles like haematopoiesis

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30
Q

What is the inside of bone like

A

Spongy/Strandy

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31
Q

Osteoid

A

Unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue

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32
Q

Layers of Bone

A

Compact Bone - Dense outer shell

Cancellous/Trabeculae Bone - Inner spongy part

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33
Q

Epiphysis

A

Expanded end of the long bones in animals

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34
Q

Diaphysis

A

Shaft or central part of a long bone

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35
Q

Periosteum

A

Membranous tissue that covers the surfaces of bones

36
Q

Describe the structure of a bone

A

Blood vessels within the compact bone

Concentric lamellae with osteocytes in lacunae connected via canaliculi all within a single trabecula

37
Q

Role of trabecular bone

A

Reduces weight
Provides space for marrow
Struts are arranged to provide maximum stress resistance

38
Q

Where might trabecular bone be found

A

Wrists
Vertebrae
Femoral Neck

39
Q

Osteoporosis

A

Thinning of cortical/compact and trabecular bone; thinned trabeculae prone to fracture

40
Q

Which sex is more affected by osteoporosis

A

Females

**Due to effect of oestrogen on bone density

41
Q

Parts of bone matrix

A

Organic/Osteoid - Strong

Inorganic - Hard

42
Q

Organic bone matrix

A

Produced by osteoblasts
Collagen I
Tensile & Compressive strength

43
Q

Role of non collagenous proteins in organic bone matrix

A

Mediating mineral deposition

44
Q

Inorganic bone batrix

A

Calcium Phosphate

Deposited in organic matrix

66% of dry weight of bone

Provides hardness of bone

45
Q

Osteogenesis Imperfecta

A

Brittle Bone Disease

Congential disease of defective collagen chain in bone causing a fragile skeleton (think of a poor organic bone matrix)

46
Q

Development of Bone cells

A

Derived from mesenchymal stem cells that differentiate into osteoprogenitor cells or chondroblasts

Osteoprogenitors differentiate into osteoblasts which lay down the organic bone matrix, mediates mineralisation of osteoid and becomes an osteocyte when syrrounded by mineralised bone

47
Q

Role of osteocytes

A

Maintaining matrix of bone

48
Q

What does osteoid secrete

A

Collagen & Matrix vesicles which contain enzymes/proteins to control Ca and PO4 availability so that mineral is precipitated

49
Q

Immature osteoid

A

Woven bone with haphazard fibre arrangement that is mechanically weak (foetal development/fracture repair)

50
Q

Mature osteoid

A

Lamellar bone; remodelled woven bone with regular parallel collagen - strong
Adult bone

Arranged as osteons aligned with direction of force

51
Q

Arrangement of Bones and Osteocytes

A

Osteocytes in concentric rings surrounding a blood vessel

Lamella

52
Q

Canaliculi

A

Microscopic canals between the lacunae of ossified bone that radiate from osteocytes

53
Q

Role of osteocytes

A

Maintaining matrix
Allowing nutrient diffusion through canaliculi
Response to tiny currents generated during bone deformity

54
Q

Osteoclasts

A

Cells that exist purely to destroy bone (only cell with this role in the body)

Bone resorbing cell that takes up calcium when needed e.g. for heart

Also for clearing bone when needed for growth or remodelling

Phagocytic in nature

55
Q

Nucleation of osteoclasts

A

Multinucleate mobile cell

56
Q

Howships Lacuna

A

Pits left behind after work of osteoclasts

57
Q

How do osteoclasts work

A

Sucking onto the bone and:

Organic: They secrete proteinases that degrade the organic matrix & collagen I

Inorganic: Pumping out H+ and essentially melting bone

58
Q

How to stimulate/reduce osteoclasts activity

A

Stimulate: Parathyroid hormone from parathyroid gland

Reduce: Calcitonin secretion from thyroid

59
Q

Bone Remodelling

A

Constant

Enables response

60
Q

What direction is new trabecula made and how are osteoclasts involved

A

In bone remodelling, new trabeculae are made in the direction of the force that the bone endures

Osteoclasts take away bone from places where there is less force in order to maintain a healthy weight

**SEEN WHEN TAKING UP A NEW SPORT

61
Q

Osteopetrosis

A

Marble/stone-bone

Rare group of inherited conditions causing defective bone remodelling due to the inability of osteoclasts to excrete sufficient H+

Brittle and easily fractured

62
Q

Clinical effects of osteopetrosis

A

Fractures, spinal nerve compression, recurrent infection due to reduced bone marrow cavity

Hepatosplenomagaly due to haematopoiesis outside bone

63
Q

Treatment of osteopetrosis

A

Bone marrow transplant to provide heathy osteoclast precursors

64
Q

Relationship between osteoblasts and osteoclasts

A

ParaThyroid Hormone (PTH) doesn’t actually directly interact with osteoclasts; instead PTH stimulates osteoblasts which have specialised receptors

Osteoblasts activate a ligand on their membrane which docks onto a receptor on osteoclast membranes, allowing them to do their shit

65
Q

Osteoprotegrin

A

Protein which prevents resorption by binding to the ligand on osteoblast surface which normally activates osteoclasts (RANKL)

66
Q

What ratio determines bone resorption

A

RANKL:Osteoprotegrin

67
Q

Factors affecting likelihood of contracting osteoporosis

A 
Disuse/Lack of activity
Genetic Factors
Nutrition
Hormones (e.g. menopause)
Aging
68
Q

What is a condition which sees higher osteoclast activity

A

Osteoporosis

69
Q

Types of bone development in the embryo

A

Intramembranous
Endochondral

**BOTH INVOLVE REPLACING A CONNECTIVE TISSUE TEMPLATE

70
Q

Intramembranous Bone Embryological Development

A

Sheets of mesenchymal stem cells differentiate into osteoblasts in centres of ossification which merge to form trabecular bone that is remodelled

Remaining mesenchyme makes bone marrow and periosteum

71
Q

Where can bone made intramembranously be found

A

Flat bones of skull, maxilla & mandible

72
Q

Endochondral Bone Embryological Development

A

Bone is formed onto a temporary cartilage model

Blood supply to shaft of bone causes osteoblast differentiation - primary centre of ossification
Following this the ends of the bone also diferenitate, allowing a long bone to eventually form

73
Q

Where can bone made endochondrally be found

A

Long Bones

74
Q

Remnant left behind by endochondral ossification

A

Epiphyseal cartilage

75
Q

Chondrocyte into Bone conversion in endochondral ossification

A

proliferating chondrocytes grow until eventually they get close enough to the centre and big enough where they die and turn into bone cells

Proliferating chondrocytes eventually stop proliferating, stopping growth

76
Q

What direction do the femur growth plates towards

A

Away from the knee (growth plates nearest knee are fastest growing)
**From the knee I flee

77
Q

What direction do the humerus growth plates towards

A

Towards the elbow (growth plate towards elbow, growth plates of proximal humerus and distal radius are fastest growing)

**To the elbows I grow

78
Q

Ossification times of carpal bones

A

Predictable sequence used for predicting bone age

Capitate & Hamate
Triquetral
Lunate
Scaphoid & Trapezium & Trapeziod
Pisiform

Cap hurts three lovers - Scorpios, Trainers and Trapeze performers

79
Q

How do bones grow width-wise

A

Bone is laid out on the outside while it is removed on the inside
e.g. on skull where space is made for the brain as it grows

80
Q

Achondroplasia

A

Dwarfism

Congenital bone disease causes by mutation on fibroblast growth factor receptor 3 (activation mutation)

This activation inhibits chondrocute proliferation, affecting growth plates
Long bone growth is stunted

Back has an inword curve, legs are bowed and extremities stunted (especially proximal)

81
Q

Substances that influence bone contribution to calcium homeostasis

A

PTH
Calcitonin
Vitamin D

82
Q

Role of PTH in Ca Homeostasis

A

Increases blood Ca while regulating Phosphate

Releases calcium from bone by indirectly stimulating osteoclasts

PTH also stimulates Vit D which enhances Ca uptake in gut
Also increases Ca & PO4 reabsorption from bone (more Oc, less Ob)

Conserving Ca in kidney while reducing reabsorption of PO4

83
Q

Role of Calcitonin in Ca Homeostasis

A

Decreasing blood Ca

  • By inhibiting osteoclast activity
  • By reducing Ca reabsorption in kidney
84
Q

Metabolic Bone Disease

A

Result from imbalance between bone formation and resorption

85
Q

Four Main Metabolic Bone Diseases

A

Osteoporosis
Rickets and Osteomalacia (lack of Vit D, inadequate bone mineralisation)
Paget’s disease (overactive osteoclasts, overactive osteoblasts respond making heavy, weak and metabolically demanding bone)
Hyperparathyroidism (PTH overstimulation of osteoclasts)

**DONT MEMORISE THE SPECIFICS THIS IS EXTRA INFORMATION

86
Q

Bone Fracture Repair until hyaline cartilage

A
  1. Periosteum is breached, haematoma and blood clot forms
  2. Replaced by vascular collagenous tissue (granulation tissue) which becomes increasingly fibrous: fibrous granulation tissue
  3. Replaced by hyaline cartilage: Firm, flexible provisional callus
87
Q

Bone Fracture Repair after hyaline cartilage

A
  1. Osteoprogenitor cells from peri & endosteum differentiate onto osteoblasts & lay down new woven bone: Bony callus
  2. Site completely bridge by bone: Bony Union
  3. Slowly remodelled to form oriented lamellar bone

Medicine 2 Week 6 - 11 (54 decks)

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