skeletal system and bones Flashcards
How does the skeletal system support the body?
structural framework for the body, attachment point for tendons of muscles
How does the skeletal system protect the body?
encloses visceral organs
How does the skeletal system provide movement in the body?
skeletal muscles attach to bone, contraction pulls on bone to produce movement
How does the skeletal system maintain mineral homeostasis in the body?
store minerals (NaCl, Ca2+), can release into blood on demand
How does the skeletal system store triglycerides in the body?
yellow bone marrow stores triglycerides
How does the skeletal system produce blood cells?
red bone marrow within bones produces red blood cells (RBCs)
Define axial skeleton
bones of head, neck and trunk
Define appendicular skeleton
- bones of limbs (incl. pectoral and pelvic girdle)
- bones are vascular and innervated
What are bones made of?
- Form of connective tissue
- extracellular matrix surrounding widely separated cells
What are the percentage components of what bones are made of?
45% organic components
55% chrystalised mineral salts
- strong and resilient: minerals resist compression, collagen resists tension
What are compact bones?
- Dense bone, forms outer shell of all bone, surrounds spongy bone
- Hollow pillars of bone matric containing nerves and blood vessels
What are spongy bones?
- looks poorly organised, BUT trabeculae aligned to assist with weight bearing
- lines of compressive stress + lines of tensile stress
- filled with red or yellow bone marrow (also medullary cavity)
classification of long bones
- longer than they are wide
- bear a lot of weight
classification of short bones
- similar width and length (cube shaped)
- stability and support with little movement
- sesamoid bones: a special type that forms in a tendon
classification of flat bones
- thin, flattened, usually a bit curved
- protect vital organs, provide surfaces for large muscle attachment
classification of irregular bones
do not fit into other categories, complicated shapes
Define diaphysis in long bones
forms the long axis of the bone
Define epiphysis in long bones
proximal and distal ends
Define articular cartilage in long bones
Hyaline (glassy appearance) cartilage covering the joint surface
Define metaphysis in long bones
regions between epiphysis and diaphysis
Define periosteum in long bones
Outer fibrous covering, double-layered membrane - entire surface except joints
Define marrow (medullary) cavity in long bones
Hollow space within diaphysis; contains yellow (fat) marrow + blood vessels
Define endosteum in long bones
Thin membrane, lines medullary cavity, internal bone surfaces, trabeculae, lines canals of compact bones
Which part of the bone has a rich blood supply?
Bone tissue + periosteum
Which arteries supply the ends of a long bone?
The epiphyseal and metaphyseal arteries supply the ends of a long bone.
What do the periosteal arteries do?
supply periosteum and outer compact bone, enter through many small canals
Where does the large nutrient artery enter a long bone?
It enters through the nutrient foramen at the center of the diaphysis.
What is the course of the nutrient artery after entering the long bone?
It enters the medullary cavity and courses toward the epiphyses.
What role do veins play in the vascular system of bones, and which structures do they accompany?
Veins carry blood away from the bone and accompany arteries.
Which part of the bone is highly sensitive to tearing and tension, and why?
The periosteum is highly sensitive to tearing and tension due to its rich sensory nerve supply.
What structures travel alongside blood vessels within bones?
Nerves travel alongside blood vessels within bones.
What are the types of cells in bone tissue?
- Osteoblasts
- Osteoclasts
What are osteoblasts?
Bone-building cells
- synthesise and secrete collagen fibres, organic components to build extracellular matrix of bone
- initiate calcification
What are osteoclasts?
Break down bone ECM (bone resorption)
- releases lysosomal enzymes + acids to digest protein and mineral components of ECM
What is the formal name for bone formation?
Ossification
From what type of tissue are all bones derived?
All bones are derived from mesenchyme, an embryonic connective tissue.
What is intramembranous ossification, and when does it occur?
Intramembranous ossification is the direct formation of bone from mesenchyme. Mesenchymal models of bone form during the embryonic period, with ossification occurring in fetal development.
What is endochondral ossification, and how does it differ from intramembranous ossification?
Endochondral ossification involves the formation of cartilage from mesenchyme during the fetal period, with the cartilage being replaced by bone.
When do cartilage models of bones form in endochondral ossification?
Cartilage models form from mesenchyme during the fetal period.
What happens during the development of the ossification center?
Mesenchymal cells cluster, differentiate into osteoblasts, and begin secreting organic extracellular matrix, forming the ossification center.
What occurs during calcification?
Calcium and other mineral salts are deposited in the extracellular matrix, causing it to harden and calcify.
How are trabeculae formed in intramembranous ossification?
The extracellular matrix develops into trabeculae, which fuse together to form spongy bone.
What leads to the development of the periosteum?
Mesenchyme at the periphery of the bone condenses and differentiates into the periosteum.
What happens during the development of the cartilage model?
Mesenchymal cells differentiate into chondroblasts, which secrete cartilage matrix, forming the cartilage model.
How does the cartilage model grow?
The cartilage model grows through the division of chondrocytes and the secretion of extracellular matrix.
How is the medullary (marrow) cavity formed?
Osteoclasts break down bone tissue in the diaphysis, creating the medullary cavity.
What occurs during the development of the primary ossification center?
In the diaphysis, bone tissue begins replacing cartilage, forming the primary ossification center.
Where do secondary ossification centers develop, and what is their function?
Secondary ossification centers develop in the epiphyses, replacing cartilage with bone tissue in these regions.
What structures form at the end of endochondral ossification, and what are they composed of?
The articular cartilage and epiphyseal plate form, both consisting of hyaline cartilage.
In which two directions does bone growth occur until around 25 years of age?
Bone grows in length (longitudinal) and diameter (appositional).
What is the function of the epiphyseal plate during bone growth?
The epiphyseal plate, initially an epiphyseal cartilage, allows bones to grow in length.
What type of bone growth occurs after 25 years of age?
Only appositional growth (increase in diameter) occurs.
What happens to the epiphyseal plate once bone length is achieved?
The epiphyseal plate ossifies, signaling the end of longitudinal bone growth.
What are the two major events involved in longitudinal bone growth?
(1) Interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate, and (2) replacement of cartilage on the diaphyseal side with bone via endochondral ossification.
What is the only way the diaphysis can increase in length?
Through the activity of the epiphyseal plate.
Does the thickness of the epiphyseal plate change during longitudinal growth?
No, the thickness of the epiphyseal plate remains constant.
How does bone length increase on the diaphyseal side of the epiphyseal plate?
Bone length increases as new bone is formed on the diaphyseal side while the cartilage is replaced by bone.
What type of bone growth does appositional growth refer to?
Appositional growth refers to growth in width or thickness.
Where is new bone deposited during appositional growth?
New bone is deposited on the outer surface of the bone.
What happens to old bone during appositional growth?
Old bone lining the medullary cavity is destroyed.
How does the medullary cavity change as bone increases in thickness?
The medullary cavity enlarges as the bone increases in thickness.
What two processes make up bone remodeling?
Bone remodeling is the combination of bone deposition by osteoblasts and bone resorption by osteoclasts.
Which cells are responsible for bone deposition in bone remodeling?
Osteoblasts are responsible for bone deposition.
Which cells are responsible for bone resorption in bone remodeling?
Osteoclasts are responsible for bone resorption.
Which vitamins and minerals are important for bone growth and remodeling?
Calcium and vitamin D (calcitriol) are important for bone growth and remodeling.
How does calcium affect bones?
Calcium hardens the bone’s extracellular matrix.
What role does vitamin D (calcitriol) play in bone health?
Vitamin D increases calcium absorption, which is essential for bone health.
How does exercise influence bone growth and remodeling?
Weight-bearing activities stimulate osteoblasts, promoting bone formation.
How do estrogen and testosterone affect bone growth and remodeling?
Estrogen and testosterone stimulate bone deposition by osteoblasts and slow bone resorption by osteoclasts.
What are the 3 types of bone markings?
- Sites of muscles and ligament attachment
- projections that help to form joints
- depressions and openings for passage of nerves and vessels
What are the sites of muscles and ligament attachments?
- tuberosity
- crest
- trochanter
- line
- tubercle
- epicondyle
- spine
- process
What are the sites of projections that help to form joints?
- head
- facet
- condyle
- ramus
What are the sites for depressions and openings for passage of nerves and vessels?
- groove
- fissure
- foramen
- notch
- meatus
- sinus
- fossa
How are bone markings for muscle attachment created?
They are created by the stress of muscles pulling on the bone.
What is an example of a bone marking created for muscle attachment?
The gluteal tuberosity on the femur is an example.
Which muscle attaches to the gluteal tuberosity on the femur?
The gluteus maximus attaches to the gluteal tuberosity.
What is the purpose of bone markings that form joints?
They have special shapes that connect bones together while still allowing movement.
Which bones articulate to form the elbow joint, and what movement is allowed?
The radius and ulna articulate with the humerus, allowing flexion and extension of the elbow.
What is the function of the foramen magnum?
The foramen magnum, located in the occipital bone, serves as a passageway for the spinal cord.
Where are bone markings for vessels and nerves commonly found?
They are found in the skull, providing passage for cranial nerves, carotid arteries, and jugular veins.
