Exam 2: Skeletal System Flashcards
What are the four classes of bones?
- Long bone
- Flat bone
- Irregular Bone
- Short bone
Name an example of long bones.
Humerus
Name an example of a flat bone.
Sternum
Name an example of an irregular bone.
Vertebra
Name an example of a short bone.
triquetral
How are the child long bone and adult long bone different?
In adults, long bones have yellow marrow in the medullary cavity while children have red bone
marrow in the medullary cavity. In adults, there is an epiphyseal line at the metaphysis, while
children have an epiphyseal plate.
Define epiphysis.
expanded ends of long bones; spongy bone surrounded by a thin layer of compact bone
Define diaphysis.
the shaft or long axis of bone; composed of a thick collar of compact bone with surrounds a medullar cavity
What is the medullary cavity?
cavity in the middle of the diaphysis that contains bone marrow; red in kids, yellow in adults
Describe hematopoiesis.
A process that occurs in the RED bone marrow and leads to the formation of blood cells and platelets
T/F: The periosteum covers the marrow cavity.
False; the endosteum covers the marrow cavity, periosteum covers the outside of the bone.
Identify the structure and name its function.
Sharpey’s fibers; they are collagen fibers that attach the periosteum to bone
What does the endosteum cover in bones?
internal surfaces such as canals
What types of cells are in the endosteum?
Osteoblasts and osteoclasts
T/F: The periosteum is double-layered.
T
What are the two layers of the periosteum and what tissue type are they made of?
- fibrous layer (irregular connective tissue)
- osteogenic layer (osteoblasts and osteoclasts)
What are the bone-forming cells?
Osteoblasts
What are the bone-resorbing cells?
Osteoclasts
What is compact bone also known as?
Lamellar bone
What is ossification?
The development of the bony skeleton from the embryonic skeleton.
What are the 2 forms of ossification?
Prenatal and postnatal
What are the two different types of bone tissue? Describe them.
- Compact bone tissue -> made of osteons (structural units of compact bone)
- Spongy bone tissue -. composed of needle like structures called trabeculae (structural units of spongy bone) -> looks like a honeycomb
T/F: Spongy bone in the epiphysis contains red bone marrow in children and adults.
T
T/F: There is no red bone marrow in the medullary cavity of adults.
T
What do Sharpey’s fibers attach together?
periosteum and compact bone
Collagen fibers run in opposite directions in adjacent lamellae to _____
resist twisting
Where are lacunae located?
Lamella
Where is blood supply found in compact bones?
Haversian canal
What are canliculi?
Tiny canals the connect lacunae to each other and to the Haversian canal to allow from transfer of substances from blood
What is the typical function of flat bones?
Protection
Where are short bones normally found?
areas where there are joints such as wrist and ankle
What is a sesamoid bone?
Specialized bone found in patellar of knee
What are embryo skeletons made of?
Cartilage; become bone after 9th week
What is a cluster of osteoblasts called?
Ossification center
Describe intramembranous ossification.
development of membrane bones such as cranial bones and clavicles. Develops from fibrous connective tissue derived from the mesenchyme
What does the bone first start out as prior to intramembranous ossification?
hyaline cartilage and fibrous connective tissue
What are the 4 steps of intramembranous ossification?
- Ossification center appears in the fibrous connective tissue membrane. -> mesenchymal cells cluster and differentiate into osteoblasts
- bone matrix (a.k.a osteoid) is secreted within the fibrous membrane-> osteoblasts secrete osteoid before becoming mineralized in a few days. the trapped osteoblasts become osteocytes
- Woven bone and periosteum form
- Bone collar of compact bone forms and red bone marrow appears
Cartilage bones that form through endochondral ossification are derived from ___
HYALINE CARTILAGE, which are produced by chondroblasts
Where can we find hyaline cartilage after endochondral ossification?
Articular cartilage and epiphyseal plates
Where are epiphyseal plates?
At the junctions of the epiphyses and the diaphysis of a long bone
What are the 5 stages of endochondral ossification?
- Bone collar forms around hyaline cartilage model.
- Cavitation of the hyaline cartilage within the cartilage model
- Invasion of internal cavities by the periosteal bud (spongy bone formation)
- Formation of the medullary cavity, appearance of secondary ossification centers
- Ossification of tthe epiphysis which restricts cartilage only to the epiphyseal plates and articular cartilages
What are the two types of postnatal ossification?
- longitudinal bone growth
- appositional bone growth
Where is hyaline cartilage added on in longitudinal bone growth? What about new bone tissue?
epiphyseal face of epiphyseal plates; diaphyseal face of epiphyseal plates
T/F: the width changes in longitudinal bone growth
F; amount of hyaline added to epiphyseal face = amount of bone tissue added to diaphyseal face
What happens in the calcification zone during bone growth?
matric begins deteriorating and becomes calcified
What happens during the proliferation zone?
Growth by increase in number of cartilage cells (epiphyseal face)
What happens in the ossification zone during longitudinal bone growth?
new bone formation
What happens during the hypertrophic zone in longitudinal bone growth?
Growth by increase in cartilage cell size
What are the 5 zones of the epiphyseal plate?
- Growth (proliferation) zone
- Hypertrophic zone
- Calcification (deterioration zone)
- Ossifcation zone
- Resorption zone
What happens in appositional bone growth?
Width and thickness of bone increase. Bone tissue is added onto the external surface and old bone is resorbed from the internal surface -> thicker but lightter bone
Explain why hormonal control of postnatal bone growth is indirect.
Growth hormone stimulates longitudinal bone growth but chondroblasts do not express growth hormone receptors
Growth hormone stimulates ____ to produce ____ to ultimately stimulate chondroblasts to produce more hyaline cartilage on the epiphyseal platte
hepatocytes; IGFs
Sex hormones ___ with growth hormone to increase IGF release
synergize
At the end of adolescence, sex hormones ___ the actions of growth hormone, leading to _____ and thus a _____
antagonize; less IGF production; Less chondroblast proliferation. this ultimately leads to decrease in hyaline cartilage production on EPIPHYSEaL FACE
How do epiphyseal plates close?
Complete ossification of the epiphyseal plates at the end of adolescence -> height is determined
Name 3 ways in which dwarfism may be caused.
- Hyposecretion of growth hormone
- Abscence of GH receptors on hepatocytes
- IGF deficiency
- No IGF receptors on chondroblastts
How does bone density in adults remain constant?
Rate of bonoe formation = rate of bone resorption
How does osteoporosis occur?
Rate of bone resorption outpaces the rate of formation
What are the functions of bone remodeling?
Maintain calcium homeostasis, allow for bone repair after fractures
In bone remodeling, ___ acts to resorp old bone
osteoclasts
In bone remodeling, ___ act to form new bone.
osteoblasts
What twto factors contrtol bone remodeling?
Hormonal control; mechanical stress
Explain hormonal control of bone remodeling
- Hypercalcemic conditions -> calcitonin is released, stimulating osteoblasts to produce bone tissue and stimulate mineralization (uses calcium from blood)
- Hypocalcemic conditions -> parathyroid hormone (PTH) is released to stimulate osteoclasts to resorp bone and release calcium from bones into the blood
What is mechanical stress based on?
Wolff’s Law
Wolff’s law states that ___
bones remodel/grow in response to mechanical stress placed on them
List some evidence that supports Wolff’s Law
- bones of the upper limb of one’s dominant arm are thicker than non-dominant
- Long bones are thickest in middle region of diaphysis (greatest bending stresses)
- Bedridden individuals lose bone density
- Bone attachment sites for muscles are thicker
What does the articular cartilage of synovial joints do?
caps the ends of bones
Function of joint cavity in synovial joints?
space that contains synovial fluid
Function of synovial fluid?
Acts as lubricant to reduce friction in synovial joints
Function of articular capsule?
double-layer with outer fibrous capsule and inner synoviam membrane
What are the 3 types of ligaments and theeir locations in synovial joints?
intrinsic -> fibrous capsule
extracapsular -> external to articular capsule
intracapsular -> deep to articular capsule (ACL)
Characteristics of menisci?
discs of fibrocartilage that extend from articular capsule into synovial cavity to minimize wear and tear
characteristics of bursae?
flattened fibrous sacs that contain synovial fluid to reduce friction where bones, tendons, ligaments, and muscles rub together
What are tendon sheaths?
elongated bursae that wrap around tendons
How does calcitriol maintain calcium homeostasis?
Acts on digestive system to more ablely absorb calcium from foods
Also can act on urinary system and make kidneys keep calcium rather than excrete it in urine
How does calcitonin mainttain calcium homeostasis?
when calcium levels arre high, calcitonin stimulates osteoblasts to build bone and prevents osteoclasts from brreaking down bone
How does PTH maintain calcium levels?
stimulates osteoclasts to break down bone to release calcium into blood
What are the 3 types of cartilage found in synovial joints?
articular cartilage, hyaline cartilage, fibrocartilage in the form of menisci
