Chapter 6 - Bone Tissue and Growth

components of skeletal system

bones, cartilage, and ligaments

support, facilitation of movement, storage of minerals, blood cells production, energy storage, and protection

functions of skeletal system

phosphates, calcium, and magnesium

main minerals in bone

yellow bone marrow

part of the bone that stores adipose cells for energy; located in the diaphysis

red bone marrow

part of bone that produces blood cells; located in the epiphyses

diaphysis

the body or shaft of a long bone; compact bone that surrounds the medullary cavity

medullary cavity

hollow part of a long bone that stores red marrow in children and yellow marrow in adults; surrounded by the diaphysis

epiphysis

the proximal and distal ends of a long bone; made of spongy bone covered by compact bone and articular cartilage

articular cartilage

hyaline cartilage pads that line joints; wear away with repeated movement and time

epiphyseal plate

part of long bone that is made of hyaline cartilage when bone is growing; ossifies when bone stops growing in length; can be seen on X-rays; also called the growth plate

epiphyseal line

part of bone that emerges when epiphyseal plate ossifies and bone stops growing in length

periosteum

the tough outer layer that covers a long bone and is absent at epiphyses; nourishes bone cells and serves at attachment site for ligaments and tendons

endosteum

lining of medullary cavity and internal spaces in long bone; where growth, repair, and remodeling occurs

consists of spongy bone between two layers of compact bone; lacks diaphysis and epiphysis

anatomy of flat bone

collagen and hydroxyapatite crystals

components of bone matrix

collagen

organic part of bone matrix that provides flexibility to bone and prevents bone from being too brittle

hydroxyapatite crystals

inorganic part of bone matrix that provides strength and stability to bone; prevents bone from being too flexible

osteogenesis imperfecta

genetic disorder in which bones make too little or defective collagen; results in brittle bones and fractures; also called brittle bone disease

osteogenic cells, osteoblasts, osteocytes, and osteoclasts

types of bone cells

osteoblasts

bone building cells; secrete bone matrix and become osteocytes when surrounded by lacunae; many connected via canaliculi

ossification

process of bone formation via appositional growth

osteocytes

primary cell of mature bone; maintain mineral content of bone; are surrounded by and trapped in matrix (lacunae)

lacunae

spaces in compact bone occupied by osteocyte body cell

canaliculi

canals in compact bone through which osteocytes communicate

osteoclasts

resorption/carving bone cell that uses enzymes and H+ ions; found on bone’s surfaces and around damaged bone; originate from WBC (monocytes and macrophages)

compact bone

dense part of bone that has few spaces; forms the solid outer layer of bone under the periosteum; found in diaphysis of long bones; provides support and protection

osteon

the structural unit of compact bone; looks like a tree trunk

spongy bone

porous and less-dense part of bone in which red bone marrow is made; located in the epiphyses of long bone; contain trabeculae

trabeculae

lines of bone in spongy bone that are oriented along lines of stress; provide structural strength

nutrient foramen

opening in diaphysis through which nerves and a nutrient artery and vein enter to supply blood to bone

intramembranous and endochondral ossification

types of bone development

intramembranous ossification

type of bone development that takes place in embryonic connective tissue (mesenchyme); found in, face, cranial vault and clavicles; is faster process of ossification; centers of ossification expand to form bone and gradually ossify the membrane

endochondral ossification

type of bone development that involves replacement of hyaline cartilage by bone tissue; found in mainly long bones and base of skull; takes longer (8wks - 20yrs)

bone replaces cartilage in diaphysis while chondrocytes build more cartilage at epiphyses of bone to increase length

process of bone growth in length

appositional growth

bone growth in width; is critical to increased bone strength

osteoblasts deposit bone under periosteum; osteoclasts erode old bone in medullary cavity

process of appositional growth

calcium, vitamin K, magnesium, vitamin c, vitamin d

vitamins and minerals that affect bone growth

contributes to bone growth and hardness

role of calcium in bone growth

necessary for calcium absorption from intestines

role of vitamins K and D in bone growth

contributes to bone structure

role of magnesium in bone growth

necessary for collagen synthesis

role of vitamin c in bone growth

Rickets

disease in which there is a lack of vitamin d in childhood; results in weakened and softer bones

osteomalacia

disease in which there is a lack of vitamin d in adulthood; leads to weakened and softer bones

growth hormone, thyroid hormone, and estrogen or testosterone

hormones affecting bone growth

growth hormone

hormone that promotes growth of bones, cartilage, and internal organs; secreted by the pituitary gland

thyroid hormone

hormone secreted by the thyroid that stimulates bone and matrix growth

acromegaly

condition in which there is excessive growth hormone production in adults; results in bigger/blockier bones

gigantism

condition in which there is excessive growth hormone production in childhood; results in extreme tallness

pituitary dwarfism

condition in which there is insufficient growth hormone production; results in very short stature

more stress, more growth

impact of mechanical stress on bone growth

bone remodeling

process in which old bone is resorbed and new bone is laid down; occurs in adult life, after injuries, and exercise

hematoma formation, callus formation, callus ossification, and bone remodeling

steps of bone repair

hematoma formation

1st step in bone repair in which a localized clot forms; results in death of osteocytes because of lack of blood flow

callus formation

2nd step of bone repair in which a mass of tissue forms at fracture site to stabilize broken bone; has internal and external layers

internal callus

part of the callus that is made of fibrocartilage matrix and into which blood vessels grow

external callus

harder part of callus that forms to stabilize each piece of bone

callus ossification

3rd step of bone repair in which the callus is replaced by spongy bone; takes several weeks to complete

bone remodeling

final step of bone repair in which the compact bone replace spongy bone at the site of fracture; can take a year to complete

displaced

term used to describe a fracture in which the ends of the bones are offset; need to be realigned

nondisplaced

term used to describe a fracture in which the ends of bones remain in anatomical alignment

open/compound

term used to describe a fracture in which one end of bone tears through the skin; has a high risk of infection

closed/simple

term used to describe a fracture in which the skin surrounding the fracture remains intact

linear

term used to describe a fracture that is parallel to the length of the bone; very small and does not go all the way through

complete

term used to describe a clean fracture that is completely through a bone

incomplete

term used to describe a fracture that is only partially through a bone

comminuted

term used to describe a fracture in which there are many tiny pieces of bone; need surgery/replacement

transverse

term used to describe a fracture that runs parallel to the length of the bone; goes all the way through

impacted

term used to describe a fracture in which a bone’s head is pushed down and crushes its neck; common in femurs

spiral

term used to describe a fracture that twists around the length of a bone

oblique

term used to describe a fracture that is at an angle to the length of the bone; goes all the way through

greenstick

term used to describe a fracture in which only one side of a bone is broken; only found in children

calcium homeostasis

balance of calcium in body; regulated by hormones

skeletal and cardiac muscle contraction; dental health; proper nerve conduction and signaling

role of calcium in body processes

parathyroid hormone

hormone secreted by parathyroid that stimulates osteoclast activity to release calcium into the blood stream

calcitriol

active form of vitamin d that stimulates absorption of calcium in small intestine

parathyroid hormone and calcitriol

hormones that increase blood calcium ion levels

calcitonin

hormone secreted by thyroid gland that inhibits osteoclast activity; stimulates calcium uptake in bones

calcitonin

hormone that decreases blood calcium ion levels

hypocalcemia

state in which there are low levels of calcium in blood; results in difficulty in blood coagulation, nerve contraction issues, and brittle bones

hypercalcemia

state in which there are high levels of calcium in blood; results in lethargy, sluggish reflexes, and constipation

parathyroid releases PTH, osteoclasts release calcium from bone, kidneys reabsorb calcium from urine, increased calcium absorption in intestines, calcium levels increase

process of fixing low calcium levels in calcium homeostasis

thyroid land releases calcitonin, osteoclast activity in inhibited, decreased calcium reabsorption in kidneys, calcium levels decrease

process of fixing high calcium levels in calcium homeostasis

osteoporosis

condition in which the bones are porous and there is a loss of bone matrix; rate of bone resorption exceeds formation; fractures are common and more likely in women due to lower hormones and little weight-bearing exercise

decrease in bone matrix and mass, increased fractures, bone deformities, and articular cartilage wear

effects of aging on skeletal system