Skeletal System Flashcards
Identify the 5 functions of the skeletal system.
- support (bones provide a framework)
- protection (vital organs are protected by the skeletal system)
- movement (shape and arrangement of bones determine what kind of movement can occur @ joints)
- storage of minerals and growth factors (stores calcium)
- hemopoiesis - blood cell production (occurs in red marrow of certain bones)
What are the four basic components of the skeletal system?
- bones
- cartilages
- ligaments
- articulations
Describe the 3 general characteristics of cartilage, paying attention to the location of perichondrium, blood vessels & nerves, and chondrocytes as well as to the general composition of the extracellular matrix.
- skeletal cartilages are highly resilient, avascular, contain no contain fibers
- a dense CT called perichondrium surrounds most hyaline and all elastic cartilage structures
- cells of cartilage tissue are chondroblasts and chondrocytes
Compare and contrast the three types of skeletal cartilage. Thinking about where each type of cartilage is located in the body, describe how the structure of each type supports its function.
Hyaline cartilage - MOST ABUNDANT , makes up articulate cartilage , makes embryonic skeleton , MOST are surrounded by perichondrium (except articulating cartilage and ET plate)
Elastic cartilage -Makes up the epiglottis (lid that covers your wind pipe) , fibers help with repeated bending , ALL are surrounded by a perichondrium
Fibrocartilage - STRONGEST , parallel rows of chondrocytes, NO PERICHONDRIUM , compressible
Identify and describe the two mechanisms of cartilage growth.
Interstitial growth - Most prominent way (the growth during childhood and adolescence)
Process: Chondrocytes undergo mitosis in lacuna surrounded by ECM. The chondroblasts (daughter cells) secrete more matrix which causes them to move apart, expanding the cartilage within.
Appositional growth - Fibroblast in deep layer of perichondrium undergo mitosis, will continue as long as skeleton grows in length.
Process: Three layers : Perichondrium, matrix, lacuna
Cells in the perichondrium differentiate into immature chondrocytes.
Immature chondrocytes secrete new matrix.
Immature chondrocytes mature into chondrocytes that live in lacuna.
Matrix enlarges, more cells are incorporated they are replaced by divisions of stem cells in the perichondrium.
Describe in a general way the bones that make up the axial skeleton? How many bones are included in the axial skeleton?
Made up of skull and vertebrae
80 bones
Describe in a general way the bones that make up the appendicular skeleton? How many bones are included in the appendicular skeleton?
Upper and lower extremities , shoulder, pelvic girdle
126 bones
Identify and describe the role of the five types of cells of bone tissue.
Derive from bone cell lineage :
- Osteogenic cells & Osteoprogenitor - ALL DERIVE FROM THIS
some become
- Osteobalst - Matrix-synthesizing cell, responsible for bone growth, trigger calsification of the bone (a process in which calcium builds up in body tissue, causing the tissue to harden.)
some become
- Osteocyte - is the mature bone cell, monitors and maintained the bone matrix , serve as mechanical stress sensor, triggers remodeling bone tissue
Derive from WBC’s:
- Osteoclast - bone destroyer , can phagosize. dead debire in the bone like a WBC , cover internal bone surfaces (protects inner bone fro osteoblast), (breaks down bone matrix and takes up mineral and secretes them on the other side of the cell) , squamous cell like appearance
Other
- Bone-lining cells - Stimulate osteoclast differentiation , prepare bone surfaces for an osteoclast to move-in
Name the organic portion of bone matrix.
osteoid
What materials make up the organic and the inorganic parts of the bone matrix?
Inorganic - mineral salts, especially hydroxyapatite (make up 50-65% of bone tissue)
- tiny packed tightly around collagen fibers which helps resist compression forces
- has calcium phosphate (helps with healthy bone development)
organic - osteoid
- makes 25 - 30% of the the matrix
- composed of ground substance and collagen fibers
(bone forms when osteoids calcify)
Which of the above materials parts of the bone matrix are primarily responsible for the tensile strength (i.e., ability to resist stretching and twisting forces between its ends) of bone? for the compression strength of bone? Which of these materials makes bone hard and heavy?
inorganic
What are the primary minerals stored by the bones?
calcium phosphate, makes hydroxyapatite (make up 50-65% of bone tissue)
What is the general function of spongy bone? of compact bone?
provides balance to the dense and heavy compact bone by making bones lighter so that muscles can move them more easily. ; It provides protection and strength to bones.
Describe the general structure of a long bone.
look at outline for explanation
articulating cartilage
epiphysis
redmarrow
epiphyseal lines
diaphysis
- medullary cavity
–endosteum (internal) covers trabeculae of spongy bone
—periosteum (external) covers external bone surfaces of the long bone
—— outer layer (made of dense irregular CT)
——inner layer
– perforating fibers (sharpeys fibers) ( intertwine with the fibers of ligaments and tendons to help anchor those structure to the bone)
Describe the medullary cavity (i.e., where is it located? what structures are found there?).
in diaphysis , site of blood cell production
Describe the structure and function(s) of the periosteum.
outer layer/ fibrous layer- dense irregular CT
inner layer/osteogenic layer - contains osteoblasts, bone lining cells, and osteoclasts
What is the function of Sharpey’s fibers (Marieb prefers to call them perforating fibers)?
tufts of collage fibers extending from the periosteum into bone matrix
intertwine with the fibers of ligaments & tendons to help anchor those structure to the bone
distribute mechanical forces over a greater surface of the bone
What is the function of nutrient foramen?
blood vessels penetrate through periosteum and pass thorough this , nutrient arteries supply the bone
What are the differences between red and yellow marrow?
red marrow - blood cell production
yellow marrow - fatty tissue
What type(s) of bone makes up the epiphyses?
compact bone externally and spongy bone internally
What is the function of the epiphyses? of the articular cartilage?
where bone growth takes place (grows from the epiphyseal plate) ; articular cartilage connects bone to another joint (shock absorber?)
What type(s) of bone makes up the diaphysis?
compact or spongy
compact bone (thickest in the middle of the shaft , thinner towards the end)
Describe the microscopic structure of compact bone, paying attention to the location of the lamellae, lacunae, osteocytes and canaliculi.
basic unit Is osteon
osteon is made of:
- lamella (matrix material that forms around the central canal)
- osteocytes in lacunae (which lie between lamellae)
- canaliculi project from lacunae
Describe the location and function of the central canals.
ridges that surround the blood vessels (made from osteoblasts)
At the center of each osteon is a central canal (also known as a Haversian canal) through which blood vessels, lymph vessels, and nerves can travel to service and signal the cells throughout the compact bone.
Describe the location and function of the perforating canals.
at the right angles of the long axis bone. connect the blood and nerve supply of the medullary cavity to the central canals (which make up the osteons)
Describe the general structure of short, flat, & irregular bones.
(compact, spongy)
consists of internal plates of spongy bone (called dipole) covered by compact bone
internal bone surfaces are covered by endosteum , external surfaces covered by periosteum
contain bone marrow but no defined marrow cavity
NO OSTEONS
How do the trabeculae of spongy bone respond to changes in the patterns of stress to which the bone is exposed?
The shape of bone changes as a result of bone remodeling corresponding to physical circumstances such as mechanical stress.
Trabeculae can become more porous and thinner
In what part of bone does blood cell production occur?
red bone marrow
Compare and contrast the microscopic structure of compact and spongy bone.
Compact bone - osteons
Spongy bone - has trabeculae ( a honey comb of small needle-like /flat pieces) open bones are filled with red or yellow bone marrow
What tissues make up the embryonic skeleton before the 6th week of development?
hyaline cartilage and fibrous membranes
Compare and contrast intramembranous and endochondral ossification.
Intramembranous - bone develops from a fibrous membrane (called a membranous bone)
Endochondral - bone develops by replacing hyaline cartilage forms everything inferior to the skull and clavicle
(called an endochondral bone)
Describe the 4 step process of intramembranous ossification.
step 1: mesenchymal cells differentiate into osteoblasts , forming the ossification center
step 2: osteoid is secreted and calcifies (promotes calcium phosphate creatin
step 3 : immature spongy bone (woven bone) and periosteum forms
- accumulating osteoid lays between embryonic blood vessels to make spongy bone
- vascularized mesenchyme condense on the external surfaces of the bone and become periosteum
step 4: spongy bone deep to periosteum are replaced by compact bone, spongy bone and red marrow develops
Describe the process of endochondral ossification.
step 1:
step 2:
Describe the process of endochondral ossification.
step 1: a bone collar forms around the diaphysis of the hyaline cartilage
process: cartilage is surrounded by perichondrium and the underneath meschenmyal cells specialize into osteoblasts. osteoblasts secrete osteoid against the hyaline cartilage diaphysis , encasing it in a bone collar. chdrroycytes within the collar enlarge (PRIMARY OSSIFICATION CENTER)
step 2: cartilage calcifies in center of diaphysis then develops cavities
hypertrophied chondrocytes clarify the cartilage matrix
cant receive nutrient so it dies creating cavities (bone collar stabilizes hyaline cartilage model)
step 3: the periosteal bud invades the internal cavities and spongy bone forms.
cavities are invaded by periosteal bud that contains the nutrient artery and vein , nerve fibers, red marrow elements, osteoprogenitor cells and osteoclasts.
osteoclast —- osteoblast that secrete osteoid and calcify reaming fragments of hyaline cartilage.
Spongy bone is formed
step 4: diaphysis elongates and medullary cavity is formed
primary ossification center enlarges and osteoclasts break down spongy bone and open up a medullary cavity
after birth
step 5: secondary ossification occurs making long bones.
the epiphyses ossify
What cells secrete osteoid?
osteoblasts
Where are the primary centers of ossification typically located? the secondary centers of ossification?
diaphysis ; epiphysis
Identify and describe the location of the hyaline cartilage structures that remain when secondary ossification is complete.
remains in articular cartilage and the epiphyseal plate after secondary ossification
How do long bones grow in length?
They grow from the epiphyseal plate
What is the function of the epiphyseal plate?
where growth of the long bone occurs
Describe the zones into which chondrocytes are organized within the epiphyseal plate.
superficial to deep
Resting Stage - Quiescent zone
Proliferating cartilage (zone) : Chondrocytes are enlarged and undergo mitosis. When the cells divide quickly, they push the epiphysis away from the diaphysis and lengthen the entire long bone.
Hypertrophic cartilage (zone) older chondrocytes are enlarging (becoming ossified)
CALCIFICATION ZONE
Ossification zone/ osteogenic zone
In which zone of the epiphyseal plate does ossification occur? Which zone exhibits a high rate of chondrocyte cell division?
ossification zone ; proliferation zone
What is the significance of epiphyseal plate closure?
longitudinal bone growth ends (when the epiphysis and diaphysis fuse)
Name and describe the process by which long bones grow in thickness/diameter.
Appositional growth
- blood vessels in the periosteum are settled in grooves made by the ridges in the periosteum
- the ridges fuse causing like a tunnel around the blood vessel ( creating endosteum lined central canal of a new osteon)
- osteoblasts in the endosteum form a new lamellae and growth proceeds towards the blood vessel
(bone grows outward)
- as bone tissue forms at the external surface of the bone, osteoclasts start eating stuff (resorption)
- as a result, bone diameter us increasing but its light so its not too heavy to move
- as bone increases in size, so does the medullary cavity
What is/are the function(s) of bone remodeling?
- remodeling is a concurrent process of bone deposit & bone respiration
- Allows bone to retain its original proportions/shape when they lengthen (a concurrent process of bone deposit and bone resorption) - osteoblasts and osteoclasts
2.bone fracture and repair
What complementary processes are involved in bone remodeling?
maintaining Ca2+ homeostasis
(helps nerves fire and muscles contract)
keeping bone strong
Describe the cellular structure of osteoclasts. What is the function of these cells?
They come from the bone marrow and are related to white blood cells. They are formed from two or more cells that fuse together, so the osteoclasts usually have more than one nucleus.
Osteoclasts are multinucleated giant cells showing specialized membrane structures, clear zones and ruffled borders, which are responsible for the process of bone resorption
How do osteoclasts break down bone matrix?
can phagosize dead bone debris
Identify and describe the 4 physiologic steps involved in the repair of bone fractures.
- A hematoma forms
blood vessels in the form and periosteum are torn. The hemorrhaged blot clots form a hematoma. Soon, bone cells that have been deprived of nutrients die and the tissue becomes swollen, painful and inflamed. - Fibrocartilaginous callus forms
Fibroblasts and chondroblasts invade the fractured site.
Fibroblasts - produce collagen fibers that connect the broken bone ends
Chondroblasts- secrete a cartilaginous matrix that bulges externally and later calcifies forming the fibrocartilaginous callus (soft callus) that spans the break and connect the broken bone ends.
- splints the broken bone - Bony callus forms.
osteoblasts begin forming spongy bone. (like endochondral ossification)
- Bone remodeling occurs.
Compact bone is laid down to reconstruct the shaft walls.
What factors can affect bone growth, repair and remodeling?
- mechanical stress induces bone remodeling
Wolfs law - bones grow or remodel in response to the physical demands placed on them
reduced mechanical stress - reduced osteoblast activity - net loss of bone mass
vs
increased mechanical stress stimulates osteoblasts - increased bone production
- hormonal controls of bone remodeling
hypocalcemia - causes hyper excitability (defects in ion channels)
hypercalcemia - causes non responsiveness and inability to functions , cause also cause kidney stones
- aging
- decreased rate of protein synthesis
- demineralization - loss of calcium and other materials from matrix
What happens to bones during prolonged periods of inactivity? Why do athletes have stronger bones than sedentary people?
leas to reduces osteoblast activity (new born formation) causing a net loss of bone mass
Where is the metaphysis? What is the functional significance of this part of the bone?
where the diaphysis and epiphysis meet. it is the epiphyseal plate in children.
contribute to bone growth
How does vitamin D influence bone structure?
helps body absorb calcium
can prevent rickets and osteomalacia (diseases from insufficient calcium)
What is the impact on the skeleton of rising levels of sex hormones at puberty?
regulates blood calcium levels, bone strength increases and skeletal maturation
What is the most important hormone regulating blood calcium levels and calcium storage in adults?
parathyroid hormone (PTH)
What is the function of parathyroid hormone? What are the target sites for the action of this hormone? What effect does parathyroid hormone have at its target sites?
When calcium levels are low, PTH is released to stimulate osteoclasts to resorb bone, releasing calcium into the bone
-decrease excretion of Ca2+ by kidneys
What is the function of calcitonin? What are the target sites for the action of this hormone? What effect does calcitonin have at its target sites?
regulates blood calcium levels by lowering the levels
- inhibits osteoclasts
- enhances mineralization of bone matrix
- increases Ca2+ excretion by kidney
How does aging affect the skeleton? At what age (approximately) do the bones of the body typically achieve their greatest density?
- decreased rate of protein synthesis
- demineralization - loss of calcium and other materials from matrix
; 25 to 30 years old
What are the anatomical landmarks for correctly measuring head circumference in children (up to 3 years old)?
measured over the most prominent part on the back of the head (occiput) and just above the eyebrows (supraorbital ridges).
What is the importance of growth assessment in children?
growth failure can be the first sign of a serious disorder
Identify factors that can cause variations in growth.
genetics
environment
race (socioeconomic status relating to nutrition)
Describe best practices for measuring growth in children 2 and under (i.e., up to 3 years) of age versus best practices for children 3 years of age and older.
under 2 - with length board
over 3 - standing
Identify normal growth rates by age.
Average Newborn - 20 inches
Growth in first year - 10 inches
Growth in second year - 5 inches
Growth each year from age 2 - 2 1/2 inche s
what is the criteria for classifying fractures
displaced vs non displaced
(is the bone in its normal position or out of its normal alignment?)
complete vs incomplete
(is it completely broken or not?)
open (compound) vs closed (simple)
(is the bone penetrating the skin or not?)
