Phase 1a revision - Bone Anatomy & Phsyiology Flashcards
(49 cards)
1
Q
What are osteogenic stem cells?
A
- Cells derived from mesenchymal stem cells and have the capacity to differentiate into osteoblasts and chondroblasts
2
Q
What are the 5 types of bone?
A
- Flat bones
- Long bones
- Irregular bones
- Short bones
- Sesamoid bones
3
Q
Where does red marrow reside in?
A
- Cancellous bone
4
Q
What are osteocytes?
A
- Osteocytes are mature osteoblasts that have been enveloped within the bone matrix
5
Q
Where do osteocytes reside?
A
- Osteocytes reside within the lacuna and communicates with surroundings by canaliculi
6
Q
What are the main functions of osteocytes (3)?
A
- Capable of bone deposition and resorption involved in bone deformation caused by muscular activity
- Strengthens bone in response to additional stresses
- Continue to form bone to an extent (maintain strength of the bone matrix)
7
Q
What is the function of the osteoblasts?
A
- Responsible for the catalysing and synthesising the mineralisation of osteoid during bone formation and remodelling
8
Q
Which cells do osteoblasts arise from?
A
- Arise from the differentiation of osteogenic cells in the periosteum – the tissue that covers the superficial surface of bone and in the endosteum (marrow cavity)
- Differentiation requires constant supply of blood
9
Q
What is the periosteum?
A
- The tissue that covers the superficial surface of bone
10
Q
What do osteoblasts secrete (5)?
A
- Alkaline phosphatase
- Colleganase
- Growth factors
- Collagen
- Osteocalcin
11
Q
What are osteoclasts?
A
- Osteoclasts are large multinucleated cells responsible for the dissolution and absorption of bone – mediators of bone destruction by phagocytosis
12
Q
Where do osteoclasts reside?
A
- Within Howship Lacunae - caused by their erosion of bone by osteoclast derived enzymes
13
Q
What are the 2 main types of bone?
A
- Immature woven (primary) bone
- Mature lamellar (secondary) bone
14
Q
How are the collagen fibres organised within woven bone?
A
- In a haphazard organisation
15
Q
What is the first type of bone formed in embryonic development and fracture healing?
A
- Primary bone - immature woven bone
16
Q
What are the two forms of mature bone?
A
- Cortical (compact) bone
- Cancellous (cancellous) bone
17
Q
Which type of bone ensheathes the bony medulla?
A
- Cortical bone
18
Q
How is cortical bone organised?
A
-
Lamellar configuration
- Densely arranged osteons (Haversian systems)
19
Q
What is an osteon?
A
- The chief structural unit of compact (cortical) bone consisting of:
- Contain a central canal that is surrounded by concentric rings (lamella) of the matrix
- Osteocytes located between lamellae within the small cavities - lacunae
- Canaliculi radiate from the launcae to the Haversian canal to provide passageways through the hard matrix
20
Q
How do the blood vessels interconnect within bone?
A
- By Volkmann’s canal
21
Q
Which cells mediate bone resorption through phagocytosis?
A
- Osteoclasts
22
Q
How do osteoclasts mediate bone resorption (3 steps)?
A
- Ruffled border (invaginations of the plasma membrane) is formed by osteoclasts, which define the active region where acid phosphatase enzymes are secreted to dissolve the organic collagen and inorganic calcium & phosphate of the bone
- Attach to the bone by osteopontin and sialoprotein forming a sealing zone between the osteoclast and bone
- Calcium hydroxyapatite crystals are removed from the bone by acidification – the osteoid is protected against osteoclastic resorption
23
Q
How is calcium stored within bone?
A
- Calcium hydroxyapetite crystals
24
Q
Which cells are predominantly found within immature woven bone?
A
- Osteocytes
25
What type of bone is the humerus?
* **Long bone**
26
What type of bone is patella?
* **Sesamoid** bone
27
Which type of collagen forms the bone?
* **Type I bone** (90%) + **Type V bone**
28
How is cancellous bone organised?
* Cancellous bone is characterised by a **trabecular structure** that is comparatively **less dense, softer, weaker and less stiff than cortical bone**
29
Where does cancellous bone reside?
* Within the **epiphysis of the bone** and within the **medullary canal**
30
What is the function of cancellous bone (2)?
* Greater surface area is ideal for **metabolic activity** - exchange of calcium ions
* High vascular and red bone marrow support **haemopoiesis**
31
What is the function of flat bones?
* **Protects internal organs**
32
What type of bone is the cranial cavity?
* Flat bone
33
What is the function of long bones?
* **Support & facilitate movement**
34
What is the function of irregular bones?
* **Vary in shape and structure**
35
What is the function of short bones?
* No diaphysis, as wide as they are long, **provide stability and some movement**
36
What is the function of sesamoid bones?
* Embedded within the tendons potentially **protects tendons from stress or wear**
37
What is the diaphysis?
* A **tubular shaft** that traverses between the proximal and distal ends of the bone
* The hollow region within the diaphysis is considered to be the **medullary cavity**
38
What does the medullary cavity encapsulate?
* Yellow marrow
39
What are the walls of the diaphysis composed of?
* **Dense and hard compact bone**
40
What is the membranous lining of the medullary cavity?
* **Endosteum**
41
What is the outer surface of the medullary cavity?
* **Periosteum**
42
Where does the red marrow occupy?
* The **cavities** of the **trabeculae** within the **epiphysis**
43
What is the epiphysis?
* **Wider terminal ends of bone** that are filled with cancellous bone
44
What is the point at which the epiphysis meets the diaphysis?
* **Metaphysis**
45
What is the metaphysis?
* **Narrow segments** that contain the **epiphyseal growth plates** - a layer of **hyaline in a growing bone**
46
What is intramembranous ossification (8 steps)?
1. **Mesenchymal cells undergo differentiation** and specialises into osteogenic cells and ultimately osteoblasts
* Clusters of osteoblasts form an ossification centre
2. **Osteoblasts secrete osteoid**, uncalcified matrix consists of collagen precursors and organic proteins which calcifies due to mineralisation - therefore **entrapping osteoblasts**
3. **Osteoblasts that are entrapped within the matrix become osteocytes**
4. As osteoblasts transform into osteocytes, osteogenic cells in the surrounding connective tissue **differentiate into osteoblasts** at the edges of growing bone
5. Clusters of osteoid unite around capillaries → **Forms a trabecular matrix**
6. Osteoblasts on the surface of newly formed spongy bone become the **cellular layer of the periosteum**
7. The periosteum secretes **compact bone** superficial to the cancellous bone
8. **Cancellous bone aggregates near blood vessels condensing into red bone marrow**
47
What is endochondral ossification?
* The **bone develops through hyaline cartilage replacement** - Behaving as a template to be completely replaced by new bone
48
Compare the rate at which intramembranous and endochondral ossification occur.
* **Endochondral** ossification is **longer** than intramembranous ossification
49
What is the process of endochondral ossification (7 steps)?
1. **Formation of matrix increases cartilaginous model size** - blood vessels in the perichondrium brings osteoblasts to the edges of the structure
2. Arriving **osteoblasts deposit osteoid** in concentric formation around the diaphysis
* Bony edges of the developing structure prevent nutrients from diffusing into the centre of the hyaline cartilage → **Chondrocyte death**
3. **Periosteal bud invasion:** Without cartilage inhibiting blood vessel invasion, **blood vessels penetrate the resulting space** - enlarging the cavities and transferring osteogenic cells with them - forming osteoblasts
* The enlarged spaces become the **medullary cavity**
4. **Chondrocytes and cartilage continue to grow at the epiphyses, increasing length**
5. Continued growth is accompanied by remodelling inside the medullary cavity, and overall **lengthening of the diaphysis**
6. **Cartilage remains at the epiphyses** and at joint surfaces as **articulate cartilage**
7. **Secondary ossification centre forms**
