Chapter 6 Flashcards
1
Q
What is bone made out of
A
Osseous tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue
2
Q
Main functions of bone
A
Support, protection, movement, store and release minerals, blood cell production, triglyceride storage
3
Q
Structure of a long bone: epiphysis
A
The ends of a long bone, made of spongy bone holding red bone marrow. Contains articulate cartilage
4
Q
Articulatr cartilage is made of _______. What is the function?
A
Hyaline cartilage
- forms joints and reduces friction
5
Q
Structure of a long bone: metaphysis
A
Between the epiphysis and diaphysis, contains the epiphyseal growth plate/line
6
Q
The epiphyseal growth plate/line is made of ________. What is the function?
A
Hyaline cartilage (turns to bone by calcification when it not longer grows)
Allows for growth in length.
7
Q
Structure of the long bone: diaphysis
A
Made of compact bone, the shaft of the long bone
Contains the periosteum, endometrium and medullary cavity
8
Q
The periosteum of the diaphysis is made up of an outer fibrous layer of _________ tissue and inner _________ layer of _____.
A
Dense irregular connective tissue
Osetogenic
Cells
9
Q
Function of the periosteum
A
Connective sheath with blood supply that surrounds the outer bone surface. Helps with bone growth, protection, repair, nourishment, and attachments
10
Q
The endosteum of the diaphysis is a single layer of ________ cells and ______ tissue that lines the medullary cavity
A
Bone forming
Connective
11
Q
The medullary cavity contains ___________ and ______.
A
Fatty yellow bone marrow
Blood vessels
12
Q
Function of the medullary cavity
A
Supply nutrients and provide strength
13
Q
Why is bone considered a connective tissue ?
A
Has a large extracellular matrix that separates cells
14
Q
What is bone extracellular matrix made of
A
Water, collagen fibres and crystallized mineral salts (like calcium phosphate and calcium hydroxide that combine to form crystals)
15
Q
Calcification is initiated by bone building cells called
A
Osteoblasts
16
Q
4 types of cells in bone tissues
A
Osteoprogenitor
Osteoblasts
Osteocytes
Osteoclasts
17
Q
Features of osteoprogenitor
A
-Develop into osteoblasts
-only bone cell that cell division occurs
-Derive from mesenchyme where connective tissues form
- found within bone blood vessel canals
18
Q
Features of osteoblasts
A
- form extracellular matrix
- synthesize and secrete collagen fibres and organic molecules
- initiate calcification and surround themselves with extracellular matrix
19
Q
Features of osteocytes
A
- osteoblasts get trapped by extracellular matrix secretions and become osteocytes
- maintains bone tissue
- matured bone cell
- metabolize in bone tissue, exchange nutrients and wastes with blood
20
Q
Features of osteoclasts
A
- resorption and breakdown of the extracellular matrix
- large cells derived from many monocytes (type of WBC)
- release lysosomal enzymes and acids that digest proteins and minerals
- part of development, maintenance and repair of bone tissue
21
Q
Osteons are found in what type of bone tissue
A
Compact bone tissue
22
Q
Trabeculae are found in what type of bone tissue
A
Spongy bone tissue
23
Q
Lamellae in compact bone tissue is a plate of ________, which surround ____________ of the central canal
A
Mineral extracellular matrix
Blood vessels and nerves
24
Q
Lamellae of spongy bone tissue is structured in
A
Irregular patterns of thin columns
25
Lacunae is between the ______ and contains
Lamellae
Osteocytes
26
Canalculi radiate from lacunae and are filled with __________ and ________ processes that _________ with eachother via gap junctions
Extracellular fluid
Osteocyte
Communicate
27
The trabeculae of spongy bone tissue contains
Red bone marrow and yellow bone marrow
28
Function of compact bone tissue
Protection and support, resist stress of weight and movement
Osteons within compact bone tissue exchange nutrients and oxygen and remove wastes
29
Function of spongy bone tissue
Allow for easy movement, support and protect red bone marrow
30
Blood vessels are abundant in bone containing red bone marrow that pass into the _________ veins and arteries, and exit through _______ and ______
Metaphyseal
Epiphysis and metaphysis
31
_______ veins and arteries exit through the periosteum
Periosteal
32
Nerves accompany blood vessels that supply bone. They are rich in the ______. _______ nerves carry pain sensation
Periosteum
Sensory
33
4 situations for ossification and osteogenesis
- FORMATION as an embryo
- GROWTH till adulthood
- REMODELLING by replacing old with new
- REPAIR when fractured
34
What is the difference between intramembranous and endochondrial ossification
Intramembraneous - bone forms directly within the mesenchyme
Endochondrial - bone forms within hyaline cartilage developed from mesenchyme
35
4 steps of intramembranous ossification
1: develop the ossification centre
2: calcification
3: trabeculae formation
4: periosteum development
36
Step 1 of intramembranous ossification: developing the ossification centre
Chemical messages cause the mesenchyme cells to cluster (this site is the ossification centre)
Mesenchyme cells then differentiate (osteoprogenitor form into osteoblasts)
37
Step 2 of intramembranous ossification: calcification
- secretion if extracellular matrix stops
- osteocytes in lacunae extend into the canalculi
- calcium mineral salts deposit and the extra cellular matrix hardens causing “calcification”
38
Step 3 of intramembranous ossification: trabeculae formation
- bone forms and develop trabeculae which fuse with another and form “spongy bone” around blood vessels
- connective tissue with blood vessels in the trabeculae differentiate into red bone marrow
39
Step 4 of intramembranous ossification: periosteum development
- mesenchyme condense at the edge of the bone to form the periosteum
- compact none replace the surface layer of spongy bone which remains in the center
40
6 steps of endochondrial ossification
1. Develop cartilage model
2. Cartilage model growth
3. Primary ossification centre development
4. Medullary cavity development
5. Secondary ossification centre development
6. Articulation cartilage and epiphyseal growth plate formation
41
Step 1 of endochondrial ossification: cartilage model development
Chemical messages cause mesenchyme cells to CROWD together and form the bones shape
- develop chondroblasts: which secrete cartilage extracellular matrix, produce a cartilage model of hyaline cartilage and perichondrium develops around the model
42
Step 2 of endochondrial ossification: growth of cartilage model
Chondroblasts bury in the extracellular matrix and become chondrocytes
Chondrocytes hypertrophy and surround the cartilage extracellular matrix causing it to calcify
The lacunae form, and chondrocytes begin to die as they can no longer diffuse through the harder matrix, when they die they leave spaces/small cavities
43
How does growth in length occur when the cartilage model grows
Interstitial endogenous growth: Cell division if the chondrocytes and secretion of cartilage extracellular matrix
44
How does growth in width occur when the cartilage model grows
Appositional exogenous growth: the deposit of extracellular matrix material on the surface of the model by new chondroblasts of the perichondrium
45
Step 3 of endochondrial ossification: developing the primary ossification centre
- Nutrient artery penetrate the perichondrium and calcify the cartilage model via nutrient foramen
- This stimulates osteoprogenitor cells to differentiate into osteoblasts
- PERICHONDRIUM becomes PERIOSTEUM when bone is formed
- periosteal capillaries grow into disintegrated calcified cartilage (promotes GROWTH of the primary ossification centre)
- primary ossification center is the SITE where BONE REPLACES CARTILAGE
- osteoblasts deposit bond extracellulsr matrix from calcified cartilage and form spongy bone trabeculae
46
Step 4 of endochondrial ossification: medullary cavity development
Osteoclasts breakdown the newly formed trabeculae replacing it with compact bone on the diaphysis wall
47
Step 5 of endochondrial ossification: secondary ossification center development
Branches of the epiphyseal artery ENTER the epiphysis
- difference from primary is that secondary proceeds outwards (from center to surface)
- spongy bone remain in the interior and there is no medullary cavity
48
Step 6 of endochondrial ossification: formation of articulation cartilage and epiphyseal growth plate
Hyaline cartilage covering the epiphysis becomes articulate cartilage
Hyaline remains at the epiphyseal growth plate and is responsible for lengthwise growth
49
Interstitial growth vs appositional growth
Interstitial: responsible for length, grows the cartilage of the epiphyseal side of the epiphyseal plate
Appositional: responsible for width which occurs in the diaphysis (in the periosteum and endosteum)
50
Length of the bone in the diaphysis side occurs by
Replacing cartilage by endochondrial ossification
51
Process of Appositional growth
Occurs at the surface
1. Periosteal cells differentiate into osteoblasts which secrete collagen fibers and form extracellular matrix
2. The osteoblasts then form into osteocytes and cream a ridge on both sides of the Periosteal blood vessels
3. The ridge enlarges and creates a groove when it folds over and fuses (tunnel) and enclosed around the blood vessel
4. Periosteum becomes endosteum
5. Osteoblasts of the endosteum form the Lamellae
6. tunnel fills and forms Osteons
7. Cycle repeats increasing the thickness of the bone
52
4 zones of bone growth for length
Resting cartilage
Proliferating cartilage
Hypertrophic cartilage
Calcified cartilage
53
Resting cartilage
Scattered chondrocytes
Anchor to epiphyseal plate
54
Proliferating cartilage
Larger chondrocytes arranged in stacks
Divide and replace dead chondrocytes in the diaphysis side and secrete extracellular matrix
55
Hypertrophic cartilage
Matured chondrocytes arranged in columns
56
Calcified cartilage
Dead chondrocytes and calcified matrix
Osteoclasts dissolve calcified cartilage
Osteoblasts and capillaries invade and replace cartilage with bone
57
What is bone remodeling
Replacing old bone tissue with new
58
What is involved in bone remodeling
Resorption and deposition
59
Bone resorption is the
Removal of mineral and collagen fibers FROM bone by OSTEOCLASTS (occurs by DESTRUCTION of extracellular matrix)
60
Bone deposition is the
ADDITION of minerals and collagen fibers TO bone by OSTEOBLASTS (FORM the extracellular matrix)
61
Process of bone resorption
1. Osteoclasts attach to surface (endosteum and periosteum) and form a leak proof seal on the ruffled border
2. Osteoclasts then release enzymes to digest collagen fibers and acids that dissolve minerals (from bone)
3. Osteoclasts forms a tunnel (like vesicle) in the old bone
4. Degraded bone minerals and proteins enter the cell (osteoclast) via Endocytosis, and cross the cell, to then exit via exocytosis on the ruffled border side
5. The dissolved substances that exit now enter the interstitial fluid to be resorbed into the blood
6. The osteoclasts then leave allowing osteoblasts to move in and rebuild bone
62
Factors that affect bone growth
minerals, vitamins, hormones, and sex hormones
63
What minerals help with bone growth
Calcium and phosphate
64
What minerals help with remodeling
Magnesium, and fluoride
65
What vitamin stimulates osteoblasts
Vitamin A
66
What vitamin helps with synthesizing collagen (main bone protein)
Vitamin C
67
What vitamin helps with building bone and absorbing calcium for bone growth
Vitamin D
68
What vitamins help with synthesizing bone proteins
Vitamin K and B12
69
How does insulin-like factors help with bone growth
-IGF stimulates osteoblasts the promote cell division and enhance protein synthesis
70
How does thyroid hormones help with bone growth
T1 and T2 stimulate osteoblasts
71
How does sex hormones help with bone growth
Estrogens and androgens
Adrenal glands produce androgens that convert to estrogen
Estrogen increase osteoblast activity and synthesis if the bones extracellular matrix (increase in activity causes growth spurts in adolescents as they have an increase in estrogen during puberty)
In adulthood sex hormones slows resorption of old bone and promotes deposition for remodeling
Estrogen slows resorption by promoting apoptosis of osteoclasts
72
Why is maintaining calcium levels important
1. Nerve and muscle cells depend on stable levels of calcium ion in extra cellular fluid to function for movement
2. Important for blood clotting
3. Enzymes rely on calcium as a cofactor
4. Any change in calcium concentration can be fatal
73
If calcium concentration is high it can
Stop the heart
74
If calcium concentration is low it can
Stop breathing
75
What is the role of bone in calcium concentration
Bone is the body’s biggest calcium reservoir
- maintains the rate of calcium being RESORBED INTO BLOOD and DEPOSITED INTO BONE
- acts as a buffer for blood calcium concentration
76
Calcium gets released into blood by ______ when levels ______
Osteoclasts
Decrease
77
Calcium gets absorbed from the blood by _______ when levels _______
Osteoblasts
Increase
78
How is calcium levels regulated
- The exchange of calcium concentration is mainly regulated by the parathyroid hormone (PTH) secreted by parathyroid glands
- PTH increase blood calcium levels when it is low via negative feedback system
- PTH also act on kidneys (effector) to decrease the loss of calcium in urine by retaining it in the blood
- PTH STIMULATE CALCITROL (a form of Vit D) to promote absorption of calcium into the GI tract from food
- can also be regulated by CALCITONIN which is secreted by parafollicular cells of the thyroid gland (inhibit activity if osteoclasts therefor increase calcium uptake and deposition)
79
Negative feedback system of low blood calcium levels: stimulus
The blood calcium levels drop
80
Negative feedback system of low blood calcium levels: receptor
Parathyroid gland cells detect the change
Which increase production of cyclic AMP
81
Negative feedback system of low blood calcium levels: input
The increase in cyclic AMP is detected intracellularly and sends signals to the control center
82
Negative feedback system of low blood calcium levels: control center
PTH gene in nucleus of parathyroid gland defects the signal of increase cyclic AMP
83
Negative feedback system of low blood calcium levels: output
increased PTH synthesis and control center releases more PTH to synthesize
84
Negative feedback system of low blood calcium levels: effector
The increase level of PTH increase the number and activity of osteoclasts
Osteoclasts act as a catalyst and speed up resorption and release more calcium into the blood from bone to stabilize levels
