Chapter 6 Slides Flashcards
Bone
organ made up of several different tissues (bone, cartilage, dense connective tissue, adipose, and nervous tissue) working together
Functions of the Skeletal System
- Provides support
- Protects the internal organs (brain, heart,
etc.) - Assists body movements (in conjunction with muscles)
- Mineral homeostasis - stores and releases calcium and phosphorus
- Participates in blood cell production (hemopoiesis/hematopoiesis)
- Stores triglycerides in adipose cells of yellow marrow
A long bone consists of
❑ Diaphysis
❑ 2 epiphyses
❑ 2 metaphyses
❑ Articular cartilage covering both epiphyses
❑ Periosteum
❑ Medullary cavity
❑ Endosteum
Bone contains an abundant
extracellular matrix
extracellular matrix
15% water, 30% collagen, and 55% crystalized mineral salts
Osteoprogenitor cells
bone stem cells able to differentiate into the other types of cells
Develops into an osteoblast
Osteoblasts
bone-building cells that secrete matrix
Forms bone extracellular matrix
Osteocytes
mature bone cells
Maintains bone tissue
Osteoclasts
remodel bones and cause them to release calcium
Functions in resorption, the breakdown of bone extracellular matrix
Compact bone
good at providing protection and support
Spongy bone
lightweight and provides tissue support
Periosteal arteries
enter the diaphysis through Volkmann’s canals. They are accompanied by periosteal veins
nutrient artery
enters the center of the diaphysis through a nutrient foramen. Nutrient veins exit via the same canal
The metaphyses and epiphyses also have their own
arteries and veins
Ossification
process of bone formation
Bones form in 4 situations
❑ During embryological and fetal development
❑ When bones grow before adulthood
❑ When bones remodel
❑ When fractures heal
Ossification takes place in 2 forms
Intramembranous and endochondral
Intramembranous ossification occurs in
flat bones when a connective tissue membrane is replaced by bone
Endochondral ossification replaces
cartilage with bone in the developing embryo and fetus
Endochondral ossification occurs in
epiphyseal plates of long bones as they grow in length
Bones thicken - thanks to
the cooperative action of osteoblasts and osteoclasts
As osteoblasts deposit bone on the outer surface, osteoclasts widen the medullary cavity from within
True
Bones store 99% of the body’s
Calcium
The parathyroid gland secretes _______ when calcium levels drop
parathyroid hormone (PTH)
Osteoclasts are stimulated to increase
bone resorption and calcium is released
PTH also stimulates the production of _______ by the kidneys to increase calcium absorption in the intestines
calcitriol
Calcitonin (CT)
secreted by parafollicular cells of the thyroid gland when calcium levels increase above normal
Osteoblasts deposit calcium in the extracellular matrix by
inhibiting bone resorption by osteoclasts
CT is an antagonist of PTH and vice versa
True
Calcium and phosphorus make
bone extracellular matrix hard
Magnesium
Helps form bone extracellular matrix
Fluoride
Helps strengthen bone extracellular matrix.
Manganese
Activates enzymes involved in synthesis of bone extracellular matrix
Vitamin A
Needed for the activity of osteoblasts during remodeling of bone; deficiency stunts bone growth; toxic in high doses.
Vitamin C
Needed for synthesis of collagen, the main bone protein; deficiency leads to decreased collagen production, which slows down bone growth and delays repair of broken bones
Vitamin D
Active form (calcitriol) is produced by the kidneys; helps build bone by increasing absorption of calcium from gastrointestinal tract into blood; deficiency causes faulty calcification and slows down bone growth; may reduce the risk of osteoporosis but is toxic if taken in high doses. People who have minimal exposure to ultraviolet rays or do not take vitamin D supplements may not have sufficient vitamin D to absorb calcium. This interferes with calcium metabolism.
Vitamins K and B12
Needed for synthesis of bone proteins; deficiency leads to abnormal protein production in bone extracellular matrix and decreased bone density.
Growth hormone (GH)
Secreted by the anterior lobe of the pituitary gland; promotes general growth of all body tissues, including bone, mainly by stimulating production of insulin-like growth factors
Insulin-like growth factors (IGFs)
Secreted by the liver, bones, and other tissues on stimulation by growth hormone; promotes normal bone growth by
stimulating osteoblasts and by increasing the synthesis of proteins needed to build new bone.
Thyroid hormones (T3 and T4)
Secreted by thyroid gland; promote normal bone growth by stimulating osteoblasts.
Insulin
Secreted by the pancreas; promotes normal bone growth by increasing the synthesis of bone proteins.
Sex hormones
(Estrogen and testosterone)
Secreted by the ovaries in women (estrogens) and by the testes in men (testosterone); stimulate osteoblasts and promote the sudden “growth spurt” that occurs during the teenage years; shut down growth at the epiphyseal plates
around age 18-21, causing lengthwise growth of bone to end; contribute to bone remodeling during adulthood by slowing bone resorption by osteoclasts and promoting bone deposition by osteoblasts.
Exercise
Weight-bearing activities stimulate osteoblasts and, consequently, help build thicker, stronger bones and retard loss of bone mass that occurs as people age.
Aging
As the level of sex hormones diminishes during middle age to older adulthood, especially in women after menopause, bone resorption by osteoclasts outpaces bone deposition by osteoblasts, which leads to a decrease in bone mass and an increased risk of osteoporosis.
Diaphysis
Bone shaft
2 epiphyses
Both ends of the bone at the joints
2 metaphyses
Region between diaphysis and epiphysis
Articular cartilage
Covers both epiphyses
Periosteum
Connective tissue surrounding the diaphysis
Medullary cavity
Hollow space within diaphysis
Endosteum
Thin membrane lining the medullary cavity
