Bone Tissue Lecture 2 Flashcards
1
Q
Bone Blood Supply Overview
A
- Rich in blood supply due to high metabolic activity and constant remodeling.
- Blood supply is crucial for maintaining structural integrity and providing nutrients.
1
Q
Arteries and Veins
Four major arteries and veins supply bone tissue:
A
- Periosteal arteries/veins
- Nutrient artery/vein
- Metaphyseal arteries/veins
- Epiphyseal artery/vein
2
Q
Periosteal Arteries/Veins
A
- Enter through Volkmann’s canals.
- Supply blood to and from the outer portion of compact bone and periosteum.
3
Q
Nutrient Artery/Vein
A
- Enter through the nutrient foramen in the diaphysis.
- Supply blood to the inner portion of compact bone and proximal spongy bone.
4
Q
Metaphyseal Arteries/Veins
A
- Enter at the metaphysis portion.
- Supply blood to the metaphysis and red bone marrow.
5
Q
Epiphyseal Artery/Vein
A
- Enter at the epiphysis portion.
- Supply blood to the epiphysis and red bone marrow.
6
Q
Bone Remodeling
Process
A
- Lifelong process
- Mature bone tissue is replaced by new bone tissue.
7
Q
Bone Remodeling
Purpose
A
- Maintains structural integrity
- Strengthens high-stress areas
- Controls reshaping after injuries
- Repairs micro-damage
- Maintains blood calcium homeostasis.
8
Q
Bone Remodeling
Bone Resorption
A
- Osteoclasts break down bone matrix.
- Removes collagen and minerals, releasing calcium into the blood.
9
Q
Bone Remodeling
Bone Deposition
A
- Osteoblasts create new bone ECM.
- Lay down osteoid, the organic bone component.
- Deposit minerals, mainly calcium, from the blood.
10
Q
Bone Remodeling
Simultaneous Processes
A
- Resorption and deposition work together.
- Respond to stress on the bone.
- Wolff’s Law: bone is added where needed and removed where not.
11
Q
Factors Affecting Bone Growth
Minerals
A
Calcium, phosphorus, fluoride, magnesium, manganese.
12
Q
Factors Affecting Bone Growth
Vitamins
A
- Vitamin A promotes osteoblasts.
- Vitamin C for collagen.
- Vitamin D aids calcium absorption.
- Vitamin K & B12 for bone proteins.
13
Q
Factors Affecting Bone Growth
Hormones
A
- Thyroid hormones (T3 & T4) promote bone growth.
- GH stimulates IGFs for growth.
- Sex hormones affect bone growth/remodeling.
- Hormones in calcium homeostasis (calcitonin, PTH).
14
Q
Calcium Functions
A
- Essential for nerve and muscle functioning.
- Key in blood clotting.
- Important for various body chemical reactions.
15
Q
Calcium Regulation
A
- Calcium levels must be tightly controlled (8.5 - 10.5 mg/dL).
Deviations can be fatal: - Hypercalcemia (>10.5 mg/dL) ➡️ Cardiac arrest.
- Hypocalcemia (<8.5 mg/dL) ➡️ Respiratory arrest.
16
Q
Calcium Regulation Locations
A
Bone:
Resorption increases blood Ca2+.
Deposition decreases blood Ca2+.
Kidney:
Reabsorption increases blood Ca2+.
Decreased reabsorption decreases blood Ca2+.
Gastrointestinal Tract:
Absorption increases blood Ca2+.
Decreased absorption decreases blood Ca2+.
17
Q
Calcium Regulating Hormones
A
- Calcitonin: Decreases blood Ca2+.
- Parathyroid Hormone (PTH): Increases blood Ca2+.
- Calcitriol (Vitamin D): Increases blood Ca2+.
18
Q
Calcitonin
A
- Produced by thyroid gland’s parafollicular cells.
- Decreases blood Ca2+.
- Antagonistic to PTH and calcitriol.
19
Q
Calcitonin Mechanism
A
- Decreases bone resorption.
- Inhibits osteoclasts, favoring osteoblasts.
- Decreases kidney Ca2+ reabsorption.
- More Ca2+ excreted, lowering blood Ca2+.
20
Q
Parathyroid Hormone (PTH)
A
- Produced by parathyroid glands.
- Increases blood Ca2+.
- Antagonistic to calcitonin, synergistic to calcitriol.
21
Q
PTH Mechanism
A
- Increases bone resorption.
- Activates osteoclasts, favoring bone breakdown.
Kidney actions:
* Increases Ca2+ reabsorption.
* Activates calcitriol.
22
Q
PTH Regulation
A
Controlled by negative feedback.
23
Q
Calcitriol
A
- Produced in skin from UV-activated cholesterol.
- Increases blood Ca2+.
- Antagonistic to calcitonin, synergistic to PTH.
24
Calcitriol Mechanism
* Increases intestinal Ca2+ absorption.
* Boosts blood Ca2+ levels.
25
Fractures
* Any break in the bone.
* Types vary by severity, location, and cause.
26
Open Fractures (Compound)
* Definition: bone ends protrude through the skin.
* Complications: infection, non-union.
* Treatment: surgery, antibiotics.
27
Closed Fractures (Simple)
* Definition: bone ends don't pierce the skin.
* May not need surgery depending on displacement.
28
Comminuted Fractures
* Bone broken in multiple places forming fragments.
* Requires surgery with internal/external fixation.
29
Greenstick Fractures
* Incomplete, one side broken, other bent.
* Common in children due to more organic material.
30
Impacted Fractures
* One bone end driven into the other.
* Common in car accidents.
31
Transverse & Oblique Fractures
* **Transverse:** perpendicular to bone length.
* **Oblique:** broken on an angle.
32
Spiral Fractures
* Looks like a corkscrew around the bone.
* Occurs due to a twisting motion.
33
Pott’s Fractures
* In distal fibula with ankle sprain.
* Serious injury to distal tibial articulation.
34
Colles’ Fractures
Distal radius fracture, distal part displaced upwards.
35
Avulsion Fractures
* Small piece of bone attached to tendon or ligament pulled away.
* Common in young athletes.
36
Stress Fractures
* Microscopic fissures due to repetitive strenuous activities.
* Commonly missed by x-rays.
37
Growth Plate Fractures
Break in child/teen growth plate can result in limb deformities.
38
Vertebral Compression Fractures (VCF)
* Vertebrae fracture, compressed into wedge shape.
* Often in osteoporosis or trauma.
39
Osteoporosis
* "Porous bone."
* Loss of bone mass with deteriorating bone microarchitecture.
* Bone resorption > bone deposition.
* Caused by: hormones, diet, exercise, drugs, genetics.
* More common in elderly and women.
40
Osteomalacia & Rickets
* Failure of bones to calcify.
* In children, Rickets; in adults, Osteomalacia.
* "Soft bones" due to calcium deficiency.
* Vitamin D, sunlight, diet deficiency.
* Rickets causes bowing, fractures; osteomalacia affects bone mineral ratio.
* Both caused by vitamin D deficiency.
41
Formation of Fracture Hematoma (Reactive Phase)
## Footnote
Fracture repair step 1
* Exposed blood vessels clot at fracture.
* Circulation stops, nearby bone cells die.
* Inflammation from dead cells.
* Phagocytes and osteoclasts remove debris.
42
Fibrocartilaginous Callus Formation
## Footnote
Fracture repair step 2
* Fibroblasts lay down collagen fibers.
* Chondrocytes produce fibrocartilage.
* Callus formation.
* Lasts about 3 weeks.
43
Bony Callus Formation
## Footnote
Fracture repair step 3
* Osteogenic cells become osteoblasts.
* Convert fibrocartilage into spongy bone trabeculae.
* Joins living and dead portions of bone fragments.
* Lasts around 3-4 months.
44
Bone Remodeling
## Footnote
fracture repair step 4
* Osteoclasts resorb remaining dead bone fragments.
* Compact bone replaces spongy bone.
* Occurs around the periphery.
45
X-Ray or Radiography
* Electron beams pass through objects.
* Soft tissue and air are translucent or black.
* Dense objects like bone, metals appear grey or white.
**Radiolucent:** Less dense, lets x-rays through.
**Radiopaque:** Dense, resists x-rays.
46
DEXA Scan (Dual X-Ray Absorptiometry)
* Measures bone density.
* Tracks bone loss and diagnoses osteoporosis.
47
Bone Scan
* Radioactive tracer taken up by living bone tissue.
* Scanning device detects high or low activity.
* **Hot Spots:** Indicate higher metabolism (e.g., cancer).
* **Cold Spots:** Indicate healed fractures, arthritis.
* Most useful bone imaging method due to efficiency, accuracy, and reduced radiation.
