Bone Tissue

How does the skeletal system support and protect the body

supports soft tissues and shields organs like brain and heart

how does the skeletal system support movement in the body

skeletal muscles contract to move at joints

how does the skeletal system provide mineral storage in the body

bone stores calcium and phosphate; mineral homeostasis

how does the skeletal system facilitate bone marrow functions

red marrow → produce RBC; yellow marrow → stores triglycerides

what are the 5 types of bone shapes

long short irregular flat and seismoid

what is the diaphysis of a long bone

shaft around medullary cavity

what are the epiphyses of a long bone

expanded proximal and distal ends

what are the metaphyses of a long bone

transition reigons between diaphysis and epiphyses; contains growth plate or adult epiphyseal line

what is the periosteum

covers outside of bone except articular surfaces

what is in the inner layer of the periosteum

osteogenic cells

articular cartilage

hyaline cartilage at joint surfaces and reduces friction and distributes load

what does red marrow support and what is it called

supports production of RBC or hemopoiesis

what does yellow marrow contain and store

contains adipocytes and stores energy

what does the adult long bone shaft typically contain

yellow marrow

where is adult red marrow concentrated

axial skeleton and the proximal humerus and femur

what makes up the organic matrix of bones and what does it do

collagen and other organic components that resist pulling and adds flexibility

what makes up the mineral component of the bones and what does it do

hydroxyapatite crystals rich in calcium and phosphate that provide hardness and resistance to compression

what do osteoprogenitor cells do

they divide and provide osteoblast precursors

what do osteoblasts do

they secrete osteoid and support mineralization

what do osteocytes do and what do they detect and facilitate

they occupy lacunae and monitor and maintain the matrix; detect mechanical conditions and facilitate remodeling

what do osteoclasts do

they reabsorb bone using acid and enzymes

what is the general rule of thumb between osteoblasts and osteoclasts

osteoblasts build and osteoclasts reabsorb

what happens when the organic matrix is damaged

the bone becomes more brittle

what happens when the mineral component is damaged

the bone becomes more flexible

where is compact bone especially thick

in the diaphysis

what does spongy bone form and why

forms internal trabeculae with spaces for marrow

what is inside one osteon

lacunae, canaliculi and the central canal

where do central canals run

they run throguh the middle of each osteon

what do performating canals connect

they connect central canals with other vascular routes

what type of lamellaw surround central canals

concentric lamellae

where are interstitial lamellae located

they occupy gaps between osteons

where are circumferential lamellae located

they encircle the cortex

what are trabeculae and what do they do

they are branching plates and beams of lamellar bone and they help carry loads with less mass

what occupies the space in between the branching plates and beams inside trabeculae

marrow

where do nutrient vessels enter from and what do they supply

enter through a nutrient foramen and supply internal reigons

what does the periosteal vessels supply and what supplies the ends

supplies outer cortex and epiphyseal and metaphyseal vessels supply the ends

what accompanies the vessels and why is this important for the periosteum

nerves accompany the vessels and the periosteum is particularly sensitive to injury

what is intramembranous ossification and what are examples of it

when bone develops in mesenchymal connective tissue (skull bones and clavicle)

what is endochondral ossification and what is formed by this route

when bone replaces hyaline cartilage model and most bones are formed via this route (including long bones)

what are the steps of intramembranous ossification

osteoblasts develop
matrix mineralizes
trabeculae
bone remodels

Endochondral ossification

cartilage model
collar and calcification
primary center ossification
secondary center ossification
growing bone

what are the steps for growth at the epiphyseal plate

resting cartilage will proliferate then chondrocytes will enlarge and then those chondrocytes will calcify before osteoblasts deposit bone there

what happens when cartilage growth ends

bone replaces the plate and leaves and epiphyseal line

what is appositional growth and how does it happen

when the shaft becomes wider
osteoblasts beneath the periosteum add matrix to the outer surface and osteoclasts reabsorb bone along the internal surface to allow the medullary cavity to enlarge

what helps maintain bone and what can happen to reduce bone mass

regular loading helps maintian bone and prolonged unloading can reduce bone mass

osteocytes can sense what

osteocytes can sense mechanical conditions and influence other bone cells

what happens as a result of osteocyte remodeling and where do we see this applied in real life

loading pattern influences where bone is changed or maintained for example orthodontic forces remodel bones around tooth sockets via coordinated resorption and formation

what is an open fracture

a wound communicates with the fracture (there is no such thing as a closed wound)

what is a comminuted fracture

the bone breaks into multiple fragments

what is an impacted fracture

fragments drive into one another

what is a greenstick fracture

an incomplete break with bending (happens in children)

how is a fracture repair

hematoma and inflammation follow vessel injury
fibrocartilaginous callus helps bridge break
bony callus of woven adn spongy bone replace soft callus
remodeling restores organized bone structure and adapts it to loading

what does calcium support in the body

muscle contraction, nerve signaling, and blood clotting

what is the pathway associated with low blood calcium

parathyroid glands increase PTH secretion when blood calcium falls
PTH promotes bone resorption indirectly and increases kidney calcium retention
PTH stimulates calcitriol formation and calcitriol increases intestinal calcium resorption
as the blood calcium recovers adn the stimulus for additional PTH secretion decreases

what cooperates in the calcium negative feedback loop

bone kidneys and intestine cooperate

what is the cacitronin feedback loop

thyroid C cells release calcitonin in response to elevated blood calcium
calcitonin can inhibit osteoclast mediated bone resorption
*less of a role in adult humans is smaller than the roles of PTH and Vitamin D

what is the role of calcium and phosphate in bone maintenance

calcium and phosphate support minrealization

what is the role of protein and vitamin C in bone maintenance

protein and vitamic C support collagen

what is the role of Vitamin D in bone maintenance

Vitamin D supports calcium absorption

what is the role of growth hormone (GH) and Insulin-like Growth Factor (IGF) in bone maintenance

GH and IGF promote growth

what is the role of sex hormones in bone maintenance

sex hormones influence the growth spurt and plate closure

what can happen post menopause after lower estrogen levels

lower estrogen can accelerate bone loss

what is osteoporosis and what can happen as a result of it

when bone mass is reduced and disrupts microarchitecture increasing fracture risk

what is osteomalacia

is the defective mineralization of osteoid in adults where bone loses the normal material stiffness