Bone Flashcards
what is bone?
Bone is an organ made up of several different tissues working together.
what tissues make up bone?
bone, cartilage, dense connective tissue, adipose and nervous tissue.
what constitutes the skeletal system?
The entire framework of bones and their cartilages
osteology
The study of bone structure and the treatment of bone disorders
what are the 6 functions of the skeletal system?
- Provides support
- Protects the internal organs (brain, heart, etc.)
- Assists body movements (in conjunction with muscles)
- Mineral homeostasis - stores and releases calcium and phosphorus
- Participates in blood cell production (hemopoiesis)
- Stores triglycerides in adipose cells of yellow marrow
Remember: “PAMPS Saves” (or “PAMPS”)
Each letter represents: P - Protects and Provides support A - Assists movement M - Mineral homeostasis P - Produces blood cells (hemopoiesis) S - Stores fat (triglycerides)
Q: What is the support function of bones?
A: Bones provide a framework for the body and attachment points for muscles
Q: How do bones provide protection?
A: Bones protect internal organs (e.g., skull protects brain, ribs protect heart and lungs)
Q: How do bones assist in movement?
A: Muscles attach to bones and contract to pull on them, enabling body movement
Q: What is the mineral function of bones?
A: Bones store and release calcium and phosphorus to maintain mineral balance
Q: What is hemopoiesis?
A: Blood cell production that occurs in red bone marrow (creates red blood cells, white blood cells, and platelets)
Q: What is stored in yellow bone marrow?
A: Triglycerides (fats) are stored as energy reserves
Q: What surrounds the cells in bone tissue?
A: An abundant extracellular matrix
Q: What are the three main components of bone’s extracellular matrix and their percentages?
A: 15% water, 30% collagen, 55% mineralized salts
Q: What is hydroxyapatite?
A: Crystals formed by the combination of calcium phosphate and calcium hydroxide
Q: What gives bone its hardness?
A: Crystallized inorganic mineral salts
Q: What provides bone its flexibility?
A: Collagen fibers
Q: What happens when bone is soaked in acid?
A: The mineral salts dissolve, leaving the bone rubbery and flexible
Q: What are the two main cell processes involving bone minerals?
A: Calcification (hardening process by osteoblasts) and breakdown (by osteoclasts)
what are the 4 types of cells that bone contains?
osteoprogenitor cells
osteoblasts
osteocytes
osteoclasts
Q: What are osteoprogenitor cells?
A: Bone stem cells that can divide and differentiate into other bone cell types
Q: What is the function of osteoblasts?
A: They are bone-building cells that secrete matrix and initiate calcification
Q: What are osteocytes?
A: Mature bone cells that maintain daily bone metabolism and cannot divide
Q: What do osteoclasts do?
A: They break down bone matrix (bone resorption) and help regulate blood calcium levels
Q: How are osteoclasts formed?
A: Through the fusion of up to 50 monocytes (white blood cells)
Q: What happens to osteoblasts when they get trapped in their own secretions?
A: They become osteocytes
Q: What do osteoprogenitor cells do?
A: They divide and develop into osteoblasts.
Q: What is the function of osteoblasts?
A: Osteoblasts build bone by secreting the bone extracellular matrix and initiating calcification.
Q: What are osteocytes?
A: Mature bone cells that maintain daily bone tissue functions.
Q: What do osteoclasts do?
A: They break down bone extracellular matrix (bone resorption) and regulate calcium levels.
Q: From which lineage do osteoprogenitor cells, osteoblasts, and osteocytes originate?
A: Bone cell lineage.
Q: From which lineage do osteoclasts originate?
A: White blood cell lineage.
Q: Why do osteoclasts have a ruffled border?
A: To release enzymes and acids for bone resorption.
Q: What is bone remodeling?
A: A continuous process of bone renewal that involves bone resorption by osteoclasts and bone deposition by osteoblasts.
Q: What are the two main processes in bone remodeling?
A:
1. Bone resorption: Removal of minerals and collagen by osteoclasts.
2. Bone deposition (formation): Addition of minerals and collagen by osteoblasts.
Q: How much of the bone mass is remodeled at any time?
A: About 5%.
Q: Why is bone remodeling important?
A:
- Removes injured bone and replaces it with new tissue.
- Adapts bone to stress, making it thicker and stronger.
- Alters bone shape for proper support.
- Makes new bone more fracture-resistant.
Q: What is the role of osteoclasts in bone resorption?
A:
Attach to bone and form a leakproof seal.
Release enzymes and acids to digest collagen and dissolve minerals.
Transport decomposed materials like calcium and phosphorus into the bloodstream.
Q: What happens after osteoclasts resorb bone?
A: Osteoblasts move in and rebuild the bone.
Q: Why do certain bones, like the distal femur, remodel faster?
A: The distal femur is replaced about every 4 months due to its higher stress levels compared to other areas of the femur that might not be fully replaced in a lifetime.
Q: What are the two main types of bone tissue?
A: 1. Compact (dense) bone 2. Spongy (trabecular/cancellous) bone
Q: What are the main characteristics of compact bone?
A:
Strongest type of bone tissue
Few spaces
Located beneath periosteum
Provides protection and support
Resists weight and movement strains
What are the main characteristics of spongy bone?
A:
Lightweight structure
Located in bone interior
Contains irregular bone lamellae
Has spaces between trabeculae
Protected by outer layer of compact bone
What is found in the spaces of spongy bone?
A:
Red bone marrow (in blood-cell-producing bones)
Yellow bone marrow (adipose tissue)
Blood vessels
Q: What are trabeculae?
A: Thin columns of bone tissue found in spongy bone
Q: Where is compact bone typically found?
A: Beneath the periosteum of all bones and makes up most of the diaphyses in long bones
Q: What are the advantages of spongy bone’s structure?
A:
Lightweight design allows easier muscle movement
Supports and protects red bone marrow
Provides internal support while maintaining lighter weight
Q: How much of the body’s calcium is stored in bones?
A: 99%
Q: What are the important functions of calcium in the body?
A:
Nerve and muscle function
Blood clotting
Enzyme activities
Preventing cardiac/respiratory arrest
Q: What is the normal blood calcium range?
A: 9-11 mg/100 mL
Q: What happens when blood calcium levels drop?
A: The parathyroid gland releases PTH (parathyroid hormone)
Q: What are the three main effects of PTH?
A: 1. Stimulates osteoclasts to release calcium from bone
2. Enhances kidney calcium retention
3. Promotes calcitriol formation for calcium absorption
Q: What is calcitonin and what does it do?
A:
Released by thyroid’s parafollicular cells
Decreases blood calcium by inhibiting osteoclasts
Increases bone calcium uptake
Q: How do bones act as a calcium buffer?
A:
Osteoclasts release calcium into blood when levels are low
Osteoblasts absorb calcium from blood when levels are high
Q: What triggers PTH secretion?
A: A drop in blood calcium levels (hypocalcemia).
Q: How does PTH affect osteoclast activity?
A: It increases osteoclast activity, which breaks down bone tissue to release calcium into the blood.
Q: How does PTH affect osteoblast activity?
A: It reduces osteoblast activity, decreasing calcium deposition into bone to conserve calcium in the blood.
Q: How does PTH influence phosphate excretion?
A: It increases urinary phosphate excretion, preventing the formation of calcium phosphate crystals (hydroxyapatite), keeping more calcium in the blood.
Q: How does PTH affect urinary calcium excretion?
A: It reduces urinary calcium excretion, conserving calcium in the blood.
Q: What is the result of PTH action on blood calcium levels?
A: Blood calcium levels return to normal, preventing hypocalcemia.
Q: Why is maintaining stable calcium levels important?
A: Stable calcium levels are essential for muscle and nerve activity, as well as other vital functions.
Q: What triggers calcitonin secretion?
A: High blood calcium levels (hypercalcemia).
Q: Which gland secretes calcitonin?
A: The thyroid gland.
Q: How does calcitonin affect osteoclast activity?
A: It reduces osteoclast activity, decreasing bone resorption and calcium release into the blood.
Q: How does calcitonin affect osteoblast activity?
A: It increases osteoblast activity, leading to more calcium being pulled from the blood and deposited into bone tissue.
Q: What is the result of calcitonin secretion?
A: Blood calcium levels decrease and return to normal.
Q: What are the overall actions of calcitonin?
A:
Reduced calcium release from bones
Increased calcium deposition into bones
Q: Why is calcitonin important?
A: It protects the body from harmful effects of excessively high blood calcium levels.
