Chapter 6: Bone Flashcards
Functions Of Bone
-protection
-structural support
-mineral storage (phosphates, calcium)(stores until needed)
-movement
-site of hematopoiesis (blood cell formation)
•hemocytoblast (in red bone marrow),red blood cells, white blood cells, platelets
-muscle and nervous tissue need calcium
Types Of Bone Tissue
Compact Bone + Spongy Bone
Compact Bone
Found in the parts of the skeleton that bear the most weight or mechanical stress
(Wall to Wall Bone matrix, minor openings, rock solid bone matrix, roughly strong as steel)
Spongy Bone
Found in the parts of the skeleton that don’t need Compact Bone
-easier to maintain (to take care of)
(Rely more a lot on diffusion to get oxygen + nutrients (glucose) (less stuff)
Spongy Bone Differs from Compact in 2 ways
- It’s lamellae (rings of bone matrix) are arranged into trabeculae, not into Osteons
- Spongy Bone does not have central canals (because it does not have osteons)
Long Bone is covered with
Like all bones, is covered with a tissue called Periosteum (around the bone) which has 2 layers:
-outer (superficial) fibrous (collagen) layers:
•site of muscle attachment
(Muscle pulls on the tissue to move the bone)
-inner (deeper) Osteogenic layer:
•contains osteoblasts (make bone tissue (matrix) ), Osteoclasts (break down bone matrix)
Long Bone is lined with
Like all bones, is lined with a tissue called Endosteum, which contains Osteoblasts (make bone tissue) + Osteoclasts (bone cell that breaks down bone tissue)
Long Bone consists of
Diaphysis- shaft of long Bone
Epiphyses- ends of bone (cap the diaphysis)
Diaphysis
Shaft of the long bone that consists of compact bone surrounding a medullary cavity
Red marrow= hemocytoblasts
Yellow marrow= fat, minerals, vitamins
(Can be a site of fat storage)
Epiphyses
Ends of the bone, each consists of a layer of compact bone covering a deeper layer of spongy bone
-each epiphysis is partially covered by an articular cartilage (shock absorbing tissue)
Short Bone
Layer of compact bone on the outside covering spongy bone on the inside
Ex: carpals (wrists)
Irregular Bone
Essentially a combination of flat + short bone
Ex: vertebrae bone (on spine)
Bone Matrix has 2 major properties
- Rigidity
- lots of collagen fibers (don’t like being bent, pulled or twisted)
- lots of GAGs
- all of the organic materials in bone matrix are called Osteoid - Hardness
- calcium salts called Hydroxyapatites (inorganic materials)
Bone matrix= Osteoid + Hydroxyapatites
Bone Development
-Embryonic Skeleton: fetal development
2 tissues - mesenchyme + hyaline cartilage (convert to bone tissue)
Mesenchyme + Hyaline cartilage —> bone ossification
Intramembranous Ossification
- conversion of mesenchyme cells into flat bone
1. mesenchyme cells become osteoblasts, which make osteoid (organic stuff in bone matrix)
2. osteoid attracts calcium which osteoblasts use to make hydroxyapatites (osteoid + hydroxyapatites = bone matrix) - as osteoblasts get trapped within matrix, they become osteocytes (bone cells)
3. trabeculae form as matrix accumulates; periosteum forms (tissue surrounding bone)
4. periosteum forms compact bone on each flat surface of spongy bone
Intramembranous Ossification: steps
- Mesenchyme cells become osteoblasts (cell that secretes matrix for bone formation), which make osteoid (organic stuff in bone matrix)
- Osteoid attracts calcium which osteoblasts use to make hydroxyapatites (osteoid + hydroxyapatites = bone matrix)
- as osteoblasts get trapped within matrix, they become osteocytes (bone cells) - Trabeculae form as matrix accumulates; periosteum forms (tissue surrounding bone)
- Periosteum forms compact bone on each flat surface of spongy bone
Endochondral Ossification
- converts cartilage into bone
- ossification of long bone
1. A periosteum forms around the cartilage and forms a BONE COLLAR of compact bone
2. In the PRIMARY OSSIFICATION CENTER, cavitation occurs: (killing cartilage)
a. chondrocytes (cartilage cells) hypertrophy (cell gets larger)
b. attraction of calcium
c. chondrocytes die and cartilage matrix decays
3. A PERIOSTEAL BUD enters the cavity and fills it with bone
4. Osteoclasts create medullary cavity
5. In SECONDARY OSSIFICATION CENTER, cavitation occurs and the cavities are filled with spongy bone
Endochondral Ossification: steps
- a PERIOSTEUM forms around the cartilage and forms a BONE COLLAR of compact bone
- in the PRIMARY OSSIFICATION CENTER, cavitation occurs: (killing cartilage)
a. chondrocytes (cartilage cells) hypertrophy (get larger)
b. attraction of calcium
c. chondrocytes die and cartilage matrix decays - a PERIOSTEAL BUD enters the cavity ad fills it with bone
- Osteoclasts create medullary cavity
- in SECONDARY OSSIFICATION CENTER, cavitation occurs and the cavities are filled with spongy bone
Longitudinal Bone Growth
increasing the length of long bone
-involves converting the growing cartilage of the epiphyseal plate into bone
Longitudinal Bone Growth Zones
- At the epiphyseal plates GROWTH ZONE, chondrocytes rapidly reproduce, thickening the plate in the direction of the epiphysis (end of bone)
- At the HYPERTROPHIC ZONE, chondrocytes enlarge, attract calcium, and die
- At the OSSIFICATION ZONE, the decaying plate cartilage is being converted into bone
Two Hormones cause + influence Longitudinal Bone Growth
- growth hormone
- thyroid hormone
Hormone That cause + influence Longitudinal Bone Growth: Growth Hormone
causes chondrocyte reproduction in growth zone
Hormone That cause + influence Longitudinal Bone Growth: Thyroid Hormone
helps set the rate of chondrocyte reproduction
-modulate the activity of growth hormone
(the more you have, the faster reproduction will occur)
Appositional Bone Growth
increase in bone thickness
-involves placing new matrix on the existing bone surfaces
-mechanical stress (or weight) activates osteoblasts(cell making matrix) and causes them to make new bone at stress points
-doesn’t stop like longitudinal bone growth
(occurs entire life time)
-epiphyseal plate closure
Bone Remodeling
-involves bone deposition + bone resorption
Bone Deposition
creation of bone matrix
-performed by osteoblast (cell making matrix)
blast-cell makes matrix
osteo- bone
Bone Resorption
the “breaking down” of bone matrix
-performed by osteoclast
clast- to break
osteo- bone
osteoclast- bone cell that breaks down bone tissue
Hormonal Regulation Of Bone Remodeling
remodeling is regulated by hormones that act to keep calcium levels in the blood at homeostasis
(keep calcium when you have it, get calcium when you need it)
(PTH) Parathyroid Hormone
activates osteoclasts (bone cell that breaks down bone tissue) to resorb bone, which releases calcium to the blood
-In conditions of hypocalcemia (low calcium in the blood), to prevent disruptions in the function of muscle + nervous tissue, the PARATHYROID GLANDS release parathyroid hormone (PTH)
