The skeletal system Flashcards
The yellow (fatty) marrow is found in the _____________ of the bone:
Diaphysis
Spongy bone is mostly found in the…
Epiphysis and metaphysis
What is the functional unit of COMPACT bone called?
An osteon
Osteocytes are arranged in concentric layers called:
Lamellae
What is the extracellular fluid called that holds an osteocyte in place?
Lacuna
What are the interconnected channels called that connect the lacuna, and what do they feed into?
Canaliculi feed into Haversian Canal
Volkmann’s canals run (perpendicular/parallel) to bone
Perpendicular
Osteogenic (osteoprogenitor) cells are in the endosteum and periosteum of growing/injured bone. What do they do?
Either differentiate into osteoblasts OR osteocytes
Osteocytes are mature bone cells that do what?
Transfer bone minerals from the interior to the growth surface
Osteoblasts are modified fibroblasts that:
Synthesize and secrete organic matrix and help calcify is. They CAN become osteocytes too!
Osteoclasts are derived from:
monocytes
What do osteoclasts do?
resorption of bone which releases CA+
The organic matrix of bone (secreted by osteoblasts) is called “Osteoid” and is made up of:
- Type 1 collagen
- Proteoglycans
- Glycoproteins
Inorganic mineral salts (mostly calcium phosphate) are part of extracellular fluid in bone and are brought in by:
osteocytes
A fetal skeleton is made up of _______________ with no minerals
Hyaline cartilage
The formation of the primary ossification center indicates:
Chondrocytes begin to hypertrophy and start secreting alkaline phosphatase
A “periosteal bud” invades the central cavity to do what?
Vascularize the tissue
The formation of the secondary ossification center indicates:
Osteoclasts are further breaking down the cavity to develop it more
What is RANKL?
a protein expressed by osteoblasts that in fact has to do with the formation, function, and survival of osteoclasts!
What is OPG (osteoprotegerin)?
Secreted by osteoblasts, inhibitor of RANKL
What does estrogen do to RANKL?
It limits production of it by osteoblasts
Where is calcitonin made?
Parafollicular cells in thyroid gland
Kidneys and GI system are also involved in _____ homeostasis:
Calcium
Low calcium levels stimulates secretion of what hormone and why?
Parathyroid hormone, because it tells osteoblasts to tell osteoclasts to increase breakdown and release of CA+
Parathyroid hormone does what to the kidneys?
Stimulates the CA+ reabsorption by kidneys and decreases phosphate reabsorption
What does calcitonin do?
Inhibits release of calcium from bone when CA+ levels are high
Post-menopausal women have lower levels of estrogen, what happens with RANKL then?
Levels of RANKL are not limited, so more is produced and more osteoclasts break away bone
Vitamin D (steroid hormone) is hydroxylated where?
In the liver and the kidneys!
Causes of Hypocalcemia:
- Hypoparathyroidism
- Vitamin D deficiency
- Chronic Kidney Disease
- renal failure
Causes of Hypercalcemia:
- Hyperparathyroidism
- cancer
- renal failure
What can happen as a result of Hypocalcemia?
- seizures
- tingling in hands/feet and around mouth because of excitability
- bronchospasm
- brittle nails/hair
- Chvostek’s sign: (tapping over facial nerve causes twitch)
- Trousseau’s sign: (BP cuff induces carpopdeal spasm)
What is hypocalcemia?
Increase in neuronal excitability
hypocalcemic tetany
What can happen as a result of hypercalcemia?
- depressed neuronal excitability (coma/confusion)
- decreased reflexes, constipation, lack of appetite
- precipitation of calcium phosphate in blood and tissues
- bradycardia
- polyuria/polydyspia
