Unit 1 Study Guide Flashcards
Compact Bone
- dense connective bone tissue
- composed of circumferential lamellae and intersitital lamellae
Spongy Bone
- located internal to compact bone
- appears porous
- composed of trabeculae and parallel lamellae
Hyaline Cartilage
- cartilage within epiphyseal plates (growth plates)
- covers the ends of some bones–called articular cartilage
- Provides a model for the function of most of the bones in the body
Fibrocartilage
- weight-bearing cartilage that withstands compression
Describe the general functions of bone.
1) Support and Protection
- structural support for entire body
- protect many delicate organs from injury/trauma (Ex: ribs-heart and lungs)
2) Movement
- Bone is the attachment site for skeletal muscles, tissues, and some organs
3) Hemopoiesis-blood cell production
- occurs in red bone marrow connective tissue that contains stem cells that form blood cells and platelets
4) Storage of Mineral and Energy Reserves
- Calcium and phosphate are stored within the bone and then released
What are some of the functions for Calcium in the body?
- muscle contraction
- blood clotting
- release of neurotransmitter from nerve cells
What are some of the functions of Phosphate in the body?
- a structural component of ATP, nucleotides, and phospholipids
- important component of the plasma membrane
What is the most common class/type of bone?
Long Bone
Label the Regions of the Long Bone
Diaphysis
- the Shaft that is made mostly of compact bone and has some spongy bone
Contains:
- Central Medularry Cavity
- Endosteum
- Periosteum
Medullary Cavity
- hollow, cylindrical spce within the diaphysis
- contains red bone marrow in children and yellow bone marrow in adults
Epiphysis
Knobby region of the long bone
- located at each end of the long bone
- composed of an outer thin layer of compact bone and an inner region of spongy bone
- the spongy bone in the epiphysis resists stress that is applied from many directions
What is the cartilage that covers the ends of each bone?
What is the purpose of this cartilage?
- Articular Cartilage-a thin layer of hyaline cartilage
- helps reduce friction and absorb shock in moveable joints
Metaphysis
- region of mature bone
- between the diaphysis and epiphysis
- contains the epiphyseal plate in growing bone (region of hyaline cartilage)
Periosteum
- double layer membrane covering external surface of bone
- attached to compact bone by perforating fibers
- outer protective layer
- inner cellular layer contains: osteoprogenitor cels, osteoblasts, osteoclasts.
What anchors the periosteum to the bone?
Perforating Fibers:
Endosteum
- an incomplete layer of cells that covers all internal surface of the bone
- Contains osteroprogenitor cells, osteoblasts, and osteoclasts
- locations
- lines medullary cavity
- lines canals
- surrounds spongy bone
Label the Flat Bone
- external surface composed of two layers of compact bone covered by periosteum
- internal surface composed entirely of spongy bone
- no medullary cavity
What is the primary component of bone?
Bone Connective tissue
Osteoprogenitor cells
- are stem cells derived from mesenchyme
- divide via cellular division and produces another stem cell and a “committed cell.”
- This commited cell matures into the osteoblast
- located in both the periosteum and the endosteum
Osteoblasts
- formed from osteoprogenitor stem cells
- synthesize and secrete osteoid
What happens to the osteoblast as the osteoid begins to calcifies?
osteoblasts become entrapped within the matrix/calcified osteoid and differentiate into osteocytes
Osteocytes
- are mature bone cells that are derived from osteoblasts after the osteoblast has lost its bone-forming ability when the matrix/osteoid is calcified
- maintain the bone matrix and detect stress on the bone
What happens if stress is dected by the osteocytes?
-osteoblasts are signaled and it may result in the deposition of new bone matrix at the surface
Osteoclasts
- large, multinuclear, phagocytic cells
- are often located within or adjacent to a lacuna
- involved in breaking down bone in bone resorption
What is the organic portion of the bone matrix?
the osteoid
composed of collegen protein plus a semisolid ground substance of proteoglycans and glycoproteins
What is the purpose of the osteoid?
to give the bone tensile strength by resisting stretching and twisting and contributing to its overall flexibility
What is the inorganic portion of the bone matrix? Purpose?
salt crystals of calcium phosphate deposited around collagen fibers
-hardens the matrix and account’s for the rigidity or relative inflexibility of bone that provide its compressional strength
Bone Formation
- begins when osteoblasts secrete the osteoid
- calcification occurs to the osteoid when hydroxyapatite crystals deposit in the bone matrix and creates inorganic portion of the bone
- initiated when the concentration of calcium ions and phosphate ions reach critical levels in the tissue
- requires vit. D, Vit C, calcium, and phosphate
Vitamin D
enhances calcium absorption from the GI tract
Vitamin C
required for collagen formation
Bone Resorption
a process where bone matrix is destroyed by substances released from osteoclasts into the extracellular space adjacent to the bone
In Bone Resorption:
What digests the organic components of the matrix?
Proteolytic enzymes released from lysosomes within the osteoclasts
In Bone Resorption:
What digests the inorganic portions of the matrix?
HCl dissolves the mineral parts (calcium and phosphate) which then enter the blood
Microscopic Anatomy of the Spongy Bone
Label:
HAS NO OSTEONS, instead is composed of Trabeculae and parallel lamellae
trabeculae
- surrounded by endosteum
- open lattice of narrow rods and plates of bone
- bone marrow fills in between
- blood vessels found within spaces
parallel lamellae
sequential rings of bone matrix
osteocytes between lamellae
canaliculi radiating from lacunae to surface
What connects osteocytes to other osteocytes?
Canaliculi
Microscopic Anatomy Of Compact Bone
Label:
What is the microanatomy of the Osteon?
Label
Concentric lamellae
in compact bone:
sequential rings of bone that surround the central canal and form the bulk of the osteon
contains collagen fibers oriented at 90 degrees from each lamellae
What is the basic functional and structural unit of the compact bone?
Osteons
Where are osteocytes found on the osteons in a compact bone?
housed in lacunae between adjacent lamellae
Lacunae
small spaces that each house an osteocyte
Canaliculi
connect to other lacunae and the central canal. permit intracellular contact and communication.
Perforating Canals
Found in Compact bone
- contains blood vessels and nerves
- Runs parallel to the central canals and help connect multiple central canals with different osteons
Circumferential Lamellae
In compact bones:
external: rings of bone immediately internal to the periosteum
internal: interal to endosteum
Interstitial lamellae
In Compact Bone:
Located:
1) between the osteons or are the left over parts that have been partially resorbed.
- interstitial lamellae are incomplete and typically have no central canal
central canal
contains blood vessels and nervous
only in compact bone
In spongy bone, what is in between each trabecullae?
Bone Marrow
Chondroblasts
- derived from mesenchymal cells and they produce the cartilage
- produce the cartilage matrix
- once they are surrounded by the matrix they prduce they become chondrocytes
Chondrocytes
occupy lacunae
-mature cartilage cells that maintain the matrix
Bone Connective Tissue vs. Hyaline Cartilage Connective tissue:
Interstitial Cartilage Growth
Occurs in the internal regions of carilage
STEPS:
1) chondrocytes housed within lacunae are stimulated to undergo mitotic division
2) Following cell division, two cells occupy a single lucana–NOW CALLED CHONDROBLASTS
3) Chondroblasts begin to synthesize and secrete new cartilage as matrix, thus pushing each other apart. They now reside in their own lacuna and are called CHONDROCYTES
4) The cartilage continues to grow in the internal regions as chondroblasts continue to produce more matrix.
Appositional Cartilage Growth
an increase in width along the cartilages outside edge, or periphery
STEPS:
1) undiferrentiated stem cells at the internal edge of the perichondrium begin to divide (perichondrium contains mesenchymal cells and stem cells)
2) The new stem cells and committed cells differentiate into chondroblasts. These chondroblasts are located at the periphery of the old cartilage–where they produce and secrete new cartilage matrix
3) The chondroblasts-as a result of the matrix formation end up pushing each other apart until they are each in their own lacuna. The cartilage continues to grow at the periphery as chondrocytes continue to produce more matrix
What happens to cartilage durng early embryonic development?
-Both interstitial and appositional cartilage growth occur simultaneously
***Interstitial growth declines rapidly, Thus growth later on primarily appositional
Ossification
formation and developement of bone connective tissue
Intramembranous Ossification
**BONE GROWTH WITHIN A MEMBRANE(mesenchyme)
-PRODUCES FLAT BONES
Steps:
1) ossification centers form within thickened regions of the mesenchyme. thickened cells in the mesenchyme divide and differentiate into osteoprogenitor cells
2) osteoprogenitor cells differentiate into osteoblasts which begin to secrete osteoid
3) Multiple ossification centers develop within the thickened mesenchyme as the number of osteoblasts increases
4) osteoid formation is followed by calcification by calcium salts being deposited onto the osteoid where they crystalize
5) Once the calcification traps the osteoblasts they differentiate into osteocytes
6) Initially woven bone is formed (inmature connective tissue)
7) the mesenchyme cells that surround the woven bone begins to thicken and forms the periosteum
8) Lamellar bone replaces the trabeculae of woven bone as compact and spongy bone form.
Endochondral Ossification
Begins with the Hyaline cartilage model
-produce LONG BONES
Steps:
1) The fetal hyaline cartilage model developes
2) cartilage calcifies and a periosteal bone collar forms. As the cartilage calcifies, blood vessels grow toward the cartilage and start to penetrate the perichondrium around the shaft
3) the primary ossification center forms in the diaphysis
4) the secondary ossification center forms in the epiphysis
5) bone replaces almost all cartilage, except the articular cartilage and epiphyseal cartilage
6) lengthwise growth continues until the epiphyseal plates ossify and form epiphyseal lines.
Appositional Bone Growth
- occurs within the periosteum
- osteoblases in the inner cellular layer of the periosteum produce and deposit bone matrix within layers parallel to the surface. Thus, the bone becomes wider as new bone is laid down at its periphery
- as this new bone is being laid down, osteoclasts along the medullary cavity resorb bone matrix,c reating an expanding medullary cavity.
Interstitial Bone Growth
- dependent upon growth of cartilage within epiphyseal plate
- similar process to endochondral ossification
In what zone of the epiphyseal plate does growth in bone length occur?
Zone 2-as chondrocytes undergo mitotic cell divison
Zone 3-as chondrocytes hypertrophy
**these combine to push the zone of resting cartilage towards epiphyseal end
What are the zones of the epiphyseal Plate?
Epiphysis
1) Zone of Resting Cartilage:
- resembles mature and healthy hyaline cartilage
- secures the epiphysis to the epiphyseal plate
2) Zone of Proliferating Cartilage
- chondrocytes undergo rapid mitotic division, enlarge slightly, and form into columns of flattened lacunae
columns are parallel to diaphysis
3) Zone of Hypertrophic Cartilage:
- Chondrocytes cease diving and begin to hypertrophy (enlarge in size)
- the walls of the lacunae become thickened because theychondrocytes resorbe matrix as they hypertrophy
4) zone of Calcified Cartilage
- minerals are deposited in the matrix between the columns of lacunae. This calcification destorys the chondrocytes and makes the matrix appear opaque
5) zone of ossification
- the walls breakdown between lacunae in the columns
- the osteoprogenitor cells and capillaries invade from the medullary cavity
- New matrix of bone is deposited on remaining calcified cartilage matrix.
Diaphysis
Bone Remodeling
The Dynamic process of continual addition of new bone tissue and removal of old bone tissue
- occurs at periosteal and endosteal surfacces of a bone
- Does not occur at the same rate everywhere in the skeleton.
- Dependent upon the coordinated activities of osteoblasts, osteocytes, and osteoclasts
Bone Resorption
removal of old bone tissue
Bone Deposition
continual addition of new bone tissue
What two factors affect bone remodeling?
Mechanical Stress
Hormones
Mechanical Stress
- occurs in the form of weight-bearing movement and exercise, and is required for normal bone remodeling
- Osteoblasts increase synthesis of osteoid, and this is followed by deposition of mineral salts.
- Bone strength increases over a period of time in response to mechanical stress.
- Results from skeletal muscle contraction and gravitational forces.
Growth Hormone
- stimulates liver to produce somatomedin
- both directly stimulate growth of cartilage in epiphyseal plate
Thyroid Hormone
- secreted by the thyroid gland
- stimulates bone growth by stimulating metabolic rate of osteoblasts
Sex Hormones
(ESTROGEN AND TESTOSTERONE)
- secreted at relatively large amounts at puberty
- stimulate osteoblasts
- promote epiphyseal plate growth and closure
Glucocorticoids
- group of steroid hormones that are released from the adrenal cortex and regulate blood glucose levels
- Increase bone loss
- in children impair bone growth when they are chronically high levels of glucocorticoids
Serotonin
-Inhibits osteoprogenitor cells from differentiating into osteoblasts when they are chronically high levels of serotonin
Calcitonin
- released from the thyroid gland in response to high blood calcium levels.
- inhibits osteoclast activity.
- stimulates the kidneys to increase the loss of calcium in the urine
parathyroid hormone
increase blood calcium levels by encouraging bone resorption by osteoclasts.
Two types of bone tissue present in skeletal bones
Compact bone
Spongy bone
Compare red and yellow bone marrow
- Red: forms blood cells and contains reticular connective tissue, immature blood cells, and fat
- in children, located in the spongy bone of most of the bones of the body as well as medullary cavity of long bones
- in adults, only found in select protion of the axial skeleton, such as flat bones of skull, vertebrae, ribs, sternum, and hip bone
- much of red bone marrow degenerates as children mature into adults and turns into yellow bone marrow
- Yellow: Fatty substance found in adults.
how parathyroid hormones and calcitroil function together
- PTH and calcitriol increase release of calcium from the bone into the blood. increase osteoclast activity
- both stimulate the kidney to excrete less calcium in the urine to increase calcium resabsorption in the tubules of the kidney
- calcitriol increases absorption of calcium from the small intestine into the blood
osteopenia
- the bones of the skeleton become weaker and thinner, resulting in insufficient ossification.
- everyone becomes slightly osteopenic
osteoporosis
- reduction in bone mass significant enough to compromise normal function
- a significant percentage of older women and a small proportion of men suffer from
4 major steps in bone repair
- a fracture hematoma forms
- a fibrocartilaginous (soft) callus forms
- a hard (bony) callus forms
- the bone is remodeled
Whose epiphyseal plate closes earlier?
females
Wolff’s Law
states that bone grows in responses to forces or demands placed on it
Fontanelles
- cranial bones interconnection by dense connective tissue forming “soft spots”.
- enable some flexion in body plates during birth and ease baby through birth canal.
Sex differences in the skull
males skulls are generally heavier, larger, longer and thicker than female skulls
- larger jaws with a more massive mastoid process and zygomatic bone
- sloped forehead
Sex Differences in the Pelvis
- female pelvis is larger and wider than males
- rounder pelvic inlet
- wider hips
- acute angle in men. obtuse angle in women
