CHAPTER 6- BONES AND BONE STRUCTURE
What is calcitriol?
active form of vitamin D
describe the position of circumferential lamellae
are found at the outer and inner surfaces of the bone, where they are covered by the periosteum and endosteum
Concept of fracture.
bone can crack or even break if it is subjected to extreme loads, sudden impacts, or stresses from unusual directions.
describe a short bone
boxy, with approximately equal dimensions EX: CARPAL (WRIST) AND TARSAL (ANKLE)
Concept of Intramembranous Ossification
bone develops directly from mesenchyme (loosely organized embryonic connective tissue) or fibrous connective tissue.
what is the most abundant mineral in the human bone?
calcium
List the inorganic components of bone matrix
calcium, potassium,sodium,magnesium,carbonate, and phosphate
function of osteoclasts
cells that absorb and remove bone matrix, They are large cells with 50 or more nuclei.
what type of bone is adapted to withstand stresses that arrive from a limited range of directions?
compact bone
Name the two types of osseous tissue
compact bone and spongy bone
what is the primary reason that accelerates osteoporosis after menopause in women?
decline in circulating estrogen.
name the different parts of the long bone
diaphysis, epiphysis,metaphysis
name the different types of ossification
endochondral ossification and intramembranous ossification
Where does growth in length occur?
epiphyseal plate
the lower end of the long bone is called _________.
epiphysis
the upper end of the long bone is called ________.
epiphysis
Name the four tissue types
epithelial, connective, muscle, nervous
what is the position of perforating canal?
extend perpendicular to the surface. AKA VOLKMANN CANAL
what is the primary source of calcitriol?
kidneys
how many cells does the lacunae hold?
lacuna never contains more than one osteocyte.
function of osteocytes
mature bone cells that make up most of the cell population 1. Osteocytes maintain the protein and mineral content of the surrounding matrix. 2. Osteocytes take part in the repair of damaged bone. If released from their lacunae, osteocytes can convert to a less specialized type of cell, such as an osteoblast or an osteogenic cell. These additional cells assist bone repair.
function of parathyroid hormone
raises blood calcium levels
Function of the calcitonin hormone.
regulate levels of calcium and phosphate in the blood,acts to reduce calcium levels in the blood
Describe long bones
relatively long and slender, consisting of a shaft with two ends that are wider than the shaft EX: FEMUR AND HUMERUS
what type of tissue reduces the weight of the skeleton?
spongy bone
Where is red bone marrow found?
spongy bone, epiphysis
What is the endosteum?
thin membrane that lines the medullary cavity passageways for blood vessels that penetrate the matrix of compact bone.
describe a flat bone
thin, parallel surfaces, which produce a flattened shape EX:STERNUM, RIBS, SCAPULAE (SHOULDER BLADES)
function of articular cartilage
to reduce friction and to prevent bony surfaces from contacting one another
What is a sesamoid bone?
usually small, round, and flat, and shaped somewhat like a sesame seed. They tend to develop within tendons EX: KNEECAPS
Is bone tissue vascular or avascular?
vascular
which vitamins are needed for proper bone formation?
vitamin D, C, A, K, B12 An adequate level of vitamin C must be present in the diet. This vitamin, which is required for certain key enzymatic reactions in collagen synthesis, also stimulates osteoblast differentiation. Vitamin A, which stimulates osteoblast activity, is particularly important for normal bone growth in children. Vitamins K and B12 are required for the synthesis of proteins in normal bone.
what condition would you observe in a child who is suffering from rickets?
vitamin d3 deficiency
Steps in the process of bone repair include:
1) Formation of a fracture hematoma. 2) Formation of a fibrocartilaginous callus. 3) Formation of bony callus 4) Remodeling the callus.
Give the 5 primary functions of the Skeletal System.
1.Support- The skeletal system provides structural support for the entire body. Individual bones or groups of bones provide a framework for the attachment of soft tissues and organs. 2. Storage of Minerals and Lipids- Minerals are inorganic ions that contribute to the osmotic concentration of body fluids.. Minerals also take part in various physiological processes, and several are important as enzyme cofactors. Calcium is the most abundant mineral in the human body. The calcium salts of bone are a valuable mineral reserve that maintains normal concentrations of calcium and phosphate ions in body fluids. In addition, the bones of the skeleton store energy in the form of lipids in yellow bone marrow, an adipose tissue that is found in certain internal bone cavities. 3.Blood Cell Production- Red blood cells, white blood cells, and other blood elements are produced in red bone marrow, which fills the internal cavities of many bones. 4.Protection- Skeletal structures surround many soft tissues and organs. The ribs protect the heart and lungs, the skull encloses the brain, the vertebrae shield the spinal cord, and the pelvis cradles digestive and reproductive organs. 5.Leverage- Many bones function as levers that can change the magnitude and direction of the forces generated by skeletal muscles. The movements produced range from the precise motion of a fingertip to changes in the position of the entire body.
what percent of calcium forms the bone?
39%
what is a lacuna?
A space within the matrix in which you would find a cell
describe the position of the concentric lamellae
Around the central canals,create a targetlike pattern, with the central canal as the bull's-eye.
Which three organs or tissues interact to assist in the regulation of calcium ion concentration in body fluids?
Bones, Intestinal tract, Kidneys
function of sex hormones
At puberty, rising levels of sex hormones (estrogen in females and testosterone in males) stimulate osteoblasts to produce bone faster than the rate at which epiphyseal cartilage expands, leading to epiphyseal closure.
Give the function of Vitamin D in relation with Calcium.
Calcium and vitamin D work together to protect your bones—calcium helps build and maintain bones, while vitamin D helps your body effectively absorb calcium
what is the location of the central canal?
Central canals generally run parallel to the surface of the bone.
the bone tissue belongs to which of the four types of tissues?
Connective more specifically supporting connective tissue
the shaft of the long bone is called ___________.
Diaphysis
Name the 4 bones that contain para nasal sinuses
FRONTAL BONE MAXILLARY BONE SPHENOIDAL BONE ETHMOIDAL BONE
function of growth hormone
Growth hormone stimulates protein synthesis and the rates of cell division and cell growth throughout the body.
what is the relation between strength of the bone and lack of exercise?
Heavily stressed bones become thicker and stronger, and bones that are not subjected to ordinary stresses become thin and brittle. For this reason, regular exercise is an important stimulus for maintaining normal bone structure
what is the effect of calcitriol on the skeletal system?
It promotes healthy bone formation by the calcification of osteoid tissue. It also directly inhibits parathyroid gland activity by decreasing parathyroid hormone synthesis and release.
list all the organic compound of bone matrix
Mostly collagen
Two types of fractures
Open fracture (compound fracture): The bone pokes through the skin and can be seen. Or a deep wound exposes the bone through the skin. Closed fracture (simple fracture). The bone is broken, but the skin is intact.
What is osteolysis?
Osteoclasts secrete acids and protein-digesting enzymes that dissolve the matrix and release the stored minerals. During this process, fingerlike processes, called the ruffled border, increase the secretory surface area of the cell in contact with the surrounding matrix. The released products are resorbed at this border. Osteolysis is an important part of the regulation of calcium and phosphate ion concentrations in body fluids.
Name all the bone cells
Osteocytes Osteoblasts Osteoprogenitor Osteoclasts
Which structure is characteristic of compact bone?
Osteon/ Haversian system is the basic functional unit of mature compact bone.In an osteon, the osteocytes are arranged in concentric layers around a vascular central canal, or Haversian canal
Name the hormones that coordinate the storage absorption and excretion of calcium ions.
Parathyroid hormone
What is calcification?
The deposit of calcium salts within a tissue.
what are the trabeculae and in which type of osseous tissue can you see it
The matrix in spongy bone forms a meshwork of supporting bundles of fibers, these thin trabeculae branch, creating an open network. The trabeculae are oriented along stress lines and extensively cross-braced
what is the position of the osteon in relation to the diaphysis?
The osteons in the diaphysis of a long bone are parallel to the long axis of the shaft.
function of osteoprogenitor cells
These stem cells divide to produce daughter cells that differentiate into osteoblasts. Osteogenic cells maintain populations of osteoblasts and so are important in the repair of a fracture AKA OSTEOGENIC CELLS
what is the structure contained within the central canal
This canal contains one or more blood vessels (normally a capillary and a venule, a very small vein) that carry blood to and from the osteon AKA HAVERSIAN CANAL
What is the periosteum?
a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.
What is rickets?
a form of osteomalacia affecting children, generally results from a vitamin D3 deficiency caused by inadequate skin exposure to sunlight and an inadequate dietary supply of the vitamin. The bones of children with rickets are so poorly mineralized that they become very flexible. The bones bend laterally, and affected individuals develop a bowlegged appearance because the walls of each femur can no longer resist the tension and compression forces applied by the body weight
What is osteoporosis?
a medical condition in which the bones become brittle and fragile from loss of tissue, typically as a result of hormonal changes, or deficiency of calcium or vitamin D.
What is osteomalacia?
a rare condition of the adult bone associated with vitamin D deficiency, resulting in decalcification and softening of bone.
describe the position of the interstitial lamellae
fill in the spaces between the osteons in compact bone, these lamellae are remnants of osteons whose matrix components have been almost completely recycled by osteoclasts
What is osteogenesis?
formation of bone AKA OSSIFICATION
what is the location of the osteoprogenitor cells?
found in periosteum and endosteum
explain the relation between gigantism and excess growth hormone prior to puberty
gigantism is a result from an overproduction of growth hormone before puberty this occurs because before puberty the epiphyseal cartilages are not yet closed and bones are still able to grow in length
What is interstitial bone growth?
growth from within,growth in length
What is appositional bone growth?
growth in bone diameter, at the surface
where are the osteoclasts more numerous?
hallow depressions called osteoclastic crypts (Howship's lacunae)
describe a irregular bone
have complex shapes EX:PELVIS AND VERTEBRAE
give examples of intramembranous ossification
he flat bones of the skull, the mandible (lower jaw), and the clavicles (collarbones).
Where is yellow bone marrow found?
in the medullary cavity of long bones
What is osteopenia?
inadequate ossification (reduction of bone mass)
from what type of cell begins the endochondral ossification
mesenchymal cells which differentiate to chondrocytes which eventually the matrix calcifies causing the death of chondrocytes and surrounding cartilage.Blood vessels invade those spaces and cells of the perichondium become osteoblasts eventually creating bone
From what type of cells begins the Intramembranous Ossification.
mesenchymal cells which differentiate to osteoblasts
the region that connects diaphysis and epiphysis is the ___________.
metaphysis
Describe Canaliculi and its function
narrow passageways through the matrix, extend between the lacunae and nearby blood vessels, forming a branching network through which osteocytes exchange nutrients, wastes, and gases.
Concept of Endochondral Ossification.
one replaces existing cartilage. Then bone growth occurs through interstitial growth (in length) and appositional growth (in width) EX:occurs mostly in long bones
Name the largest bone cells.
osteoclasts
Name the mature bone cells.
osteocytes
name the most abundant bone cell
osteocytes
what type of cell is found in the lacunae?
osteocytes
what is the non-pathological loss of bone that occurs with aging?
osteopenia
What is ossification?
physical process of bone formation
function of osteoblasts
produce new bone matrix, Osteoblasts make and release the proteins and other organic components of the matrix.
function of red bone marrow
produce red blood cells
function of thyroxine
stimulates cell metabolism and increases the rate of osteoblast activity.
function of yellow bone marrow
stores fat for energy
What is the epiphyseal plate?
the cartilaginous region between the epiphysis and diaphysis of a growing bone, aka epiphyseal cartilage
what are epiphyseal lines?
the former location of this cartilage can often be seen in x-rays as a narrow,which remains after epiphyseal closure