The skeletal system Flashcards
List three functions of five of the skeletal system
I. Provides structure, support, and protection
II. Crucial for locomotion and movement
III. Site of blood cell formation
IV. Storehouse for some inorganic minerals (ex. calcium)
V. Indicates sex, height, weight, race, and medical history
List the bones of the body by shape
Long, short, flat, irregular, pneumatic, and sesamoid bones
Where are pneumatic bones located and what is their function?
They are bones only of the skull and reduce the weight it
Where are sesamoid bones located and what is their function?
They’re located within a tendon and change the angle of muscle attachment for more mechanical leverage.
Axial VS Appendicular skeleton
- Bones of the skull, hyoid, vertebral column, and rib cage are Axial.
- Bones of the limbs and their attachments to the axial skeleton are appendicular.
Cranial VS Post-Cranial
- Bones of the skull are cranial
- Bones of the rest of the skeleton are post-cranial
Diaphysis
bone shaft; primary ossification center
Epiphysis
Usually an area of articulation or site of high muscle tension; secondary ossification center
Epiphyseal plate (disk)
Separates the diaphysis from epiphysis; made of hyaline cartilage
Periosteum
Dense connective tissue covering outer surface but not articular surfaces
List the two layers of the periosteum
I. Outer fibrous
II. Inner cellular layer
List the components of the periosteum layers
Outer fibrous: type I collagen fibers, fibroblasts, blood vessels, and nerve fibers
Inner Cellular layer: primarily osteoprogenitors and osteoblasts
List the function and components of the Endosteum
It’s a thin layer that covers inner bone surfaces; primarily osteoprogenitors and osteoblasts
What is the medullary cavity (marrow cavity)?
cavity at the center of long bones
Where can articular cartilage be found and what is it composed of?
It covers articular surfaces and is hyaline cartilage
What is the matrix composed of?
Type I collagen fibers and ground substance
What are the fibers of the matrix composed of and what are their functions?
Type I collagen fibers and they provide strength to tensile forces (being stretching)
What is the ground substance of the matrix composed of?
An organic component: proteoglycans (chondroitan and keratan sulfate, and hyaluronic acid) and glycoproteins (osteonectin and osteocalcin)
An inorganic component: hydroxyapatite; a mineral composite that gives strength to resist compressive forces
Osteoprogenitors give rise to what and can be found where?
They give rise to osteoblasts and are found in the cell layers of the periosteum and endosteum.
Osteoblasts give rise to what, can be found where, and do what?
They give rise to osteocytes and are located in central and perforating canals of the periosteum and endosteum. They lay down new bone.
Osteocytes are located where and do what?
They are in lacunae of compact bone, and the bony struts of spongy bone. They maintain bone tissue and regulate mineral content.
What are osteoclasts and what is their function?
large multinucleated cells stemming from several monocytes. They destroy bone cells.
There are two types of bone tissue, list them.
Primary bone tissue (woven bone; immature) and Secondary bone tissue (mature or lamellar bone)
List the characteristics of primary bone
I. Arises during fetal development.
II. Associated with fracture repair
III. Collagen fibers randomly arranged, lower mineral content, has a higher amount of osteocytes
List the components of secondary bone (compact bone)
I. An outer layer of densely packed bone tissue
II. osteons
III. circumferential lamellae
IV. interstitial lamellae
What are osteons?
They are the main unit of compact bones. They are cylindrical and make up the interior layer.
Lamellae is associated with osteons, describe it
They have concentric layers of bony connective tissue in which the fibers run at right angles to adjacent layers
Describe the central canal
Holds vascular structures and nerves
Describe lacunae
Holes between lamellae
Describe canaliculi
Paths connecting lacunae and central canals to eachother
Describe perforating canals
Connect central canals and the exterior with interior
Describe circumferential lamellae and list its two components
Multiple layers of mineralized matrix. It has an external and internal lamellae.
The location of the external circumferential lamellae
immediately deep to the periosteum
The location of the internal circumferential lamellae
the perimeter of the medullary cavity
Describe interstitial lamellae
layers of mineralized matrix between osteons; the remains of osteocytes
Describe spongy bone and where is it located?
It is a network on bony struts and bars consisting of a few layers of concentric bony connective tissue. It is located on the interior of bone. (blood cells form in spongy bone)
Describe subchondral bone and where is it found?
It is a thin layer of modified compact bone that is almost avascular and is shiny or glossy on bone. It can be found at articular surfaces.
What is Wolff’s Law?
Bone grows in accordance to how force is transmitted through it
List the two types of developmental bone growth
Intramembranous (dermal) and endochondral (cartilaginous) bone
What bones are intramembranous?
Bones of the top of the skull and the calvicle
What bones are endochondral?
Bones of the skull base, all post-cranial bones, and part of the clavicle. (the clavicle has dual origins)
Describe the ontogenetic process in endochondral bone
- A cartilaginous model made of hyaline cartilage forms
- It then disintegrates and carves interior as it degrades; blood vessels then invade along with mesenchymal cells
- Osteoblasts then form from the mesenchymal cells and start forming spongy bone
- Periosteum forms; its cell layer’s osteoblasts form compact bone
- Growth then takes place in two directions between the diaphysis and epiphysis (interstitial growth)
Describe interstitial growth
Blood vessels invade ends of bone, which become secondary ossification centers. These centers are the epiphyseal plates and are centers of active growth. Growth ceases when the plate ossifies around puberty.
Describe appositional growth
Increase in over all size. Occurs in tandem with interstitial growth. osteoblasts lay compact bone just below the periosteum. Osteoclasts work on inner bone destroying bony connective tissue this enlarging the medullary cavity if present. The compact/spongy bone interface is thus remodeled.
Describe the ontogenetic process in intramembranous bone
- Membranes form around blood vessels
- Undifferentiated connective tissue near blood vessels differentiate into osteoblasts, which form spongy bone
- Periosteum forms: osteoblasts form from cell layer and form compact bone below periosteum
- Remaining growth occurs in a way similar to appositional growth of endochondral bone
Which vitamins, if low in concentration, could cause deficiencies in bone?
Vitamin C and D
What is Vitamin C necessary for and what can a deficiency lead to?
It is needed for proper collagen and osteoblast function. A low amount of vitamin C can lead to scurvy.
What is scurvy?
It is the thinning of compact bone, and the bony struts of spongy bone.
What is the function of Vitamin D in bone?
It maintains bone mineralization and increase calcium absorption and re-absorption in the small intestines and kidneys
How can one acquire vitamin D?
Through exposure to UV rays and through food
What hormone facilitates the transition of the vitamin d precursor, 7-dehydrocholesterol, to 1,25-dihydroxycholecalciferol, the active form of vitamin d?
Parathyroid hormone
Rickets and osteomalacia are a result of what?
Insufficient amounts of vitamin D
In children, bowed lower limbs are a sign of what?
Rickets
Name the two hormones involved in bone growth
parathyroid hormone and pituitary growth hormone
Which hormone increases blood calcium levels by indirectly stimulating osteoclasts?
parathyroid hormone
What is released when PTH binds to osteoblasts?
osteoprotegerin ligand (OPGL)
What effect does OPGL have have preosteoclasts?
It causes them to mature into osteoclasts
What breaks down bone tissue?
osteoclasts
Describe the process by which osteoclasts break bone down
They first secrete acid which degrades the mineral component. Then, lysosomes then secrete enzymes which digest collagen fibers and the organic component of the ground substance.
What can excess PTH lead to?
bone thinning due to excessive osteoclast activity and decreased osteoblast activity.
What hormone causes gigantism in children and acromegaly in adults?
pituitary growth hormone (GH)
What type of growth is seen in acromegaly and where?
endochondral and some intramembranous bone see appositional (increase in overall size) bone growth; the tarsals, carpals, the mandible, and nose cartilage are most notable.
Describe a greenstick fracture
the bone is bent with an incomplete fracture on the convex side; due to less mineralization in children (think of a stick off of a tree that is still green and how they don’t break very easily).
Describe a comminute fracture
A complete fracture that results in the fragmentation of the bone. If the area of the bone doesn’t receive a good blood supply healing could be very slow and result in the necrosis of osteocytes
Describe a compression fracture
compressive forces cause a bone to collapse on itself; typically seen in long bones and vertebrae
Describe the healing of a fracture
I. a fracture hematoma forms from a ruptured blood vessel
II. A soft callus then forms (a mix of spongy bone (from osteoblasts) and fibrocartilage (from fibroblasts))
III. A hard callus forms as a result of the soft callus mineralizing
IV. The hard callus then remodels into mature bone
-fracture healing is the same for all fractures
