51 Questions
What is the role of plasma proteins in binding with Ca2+?
They are more ionized at high pH
How much Ca2+ is exchanged between plasma and the stable pool of bone calcium per day?
7.5 mmol
What regulates the distal tubular reabsorption of Ca2+ in the kidneys?
PTH
How much of the filtered Ca2+ in the kidneys is reabsorbed?
98-99%
What is the active form of vitamin D that is also called calcitriol?
1,25-dihydroxycholecalciferol
How is vitamin D3 mainly produced in mammals?
By the action of ultraviolet light on 7-dehydrocholesterol
Where does the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol mainly occur?
In the proximal tubules of the kidneys
Which protein transports vitamin D3 and its hydroxylated derivatives in the plasma?
Vitamin Dbinding protein (DBP)
Which form of calcium is a vital second messenger in the body fluids?
Ionized calcium (Ca2+)
What is the consequence of a decrease in extracellular Ca2+ in vivo?
Hypocalcemic tetany
Why is it important to know the plasma protein level when evaluating total plasma calcium?
To understand the extent of Ca2+ binding by plasma proteins
How do symptoms of tetany vary with changes in total calcium levels?
Increased total calcium levels worsen tetany symptoms
Which compounds in the body contain phosphate?
ATP, cyclic adenosine monophosphate (cAMP), and many proteins
Where is 85-90% of the total body phosphorus found?
In the skeleton
How much phosphorus normally enters bone per kg per day?
3 mg
What is the main site of Pi reabsorption in the kidney involving sodium-dependent Pi cotransporters?
Proximal tubule
What is the primary action of parathyroid hormone (PTH) in calcium homeostasis?
Mobilize calcium from bone
Which hormone is derived from vitamin D and plays a significant role in calcium homeostasis?
1,25-Dihydroxycholecalciferol
What is the main function of calcitonin in calcium metabolism?
Inhibit bone resorption
Which organs or tissues respond to changes in extracellular calcium concentrations by mobilizing, excreting, or taking up calcium?
Kidneys, bones, intestine
What stimulates calcitonin secretion in the body?
Gastrin
Where are the receptors for calcitonin found in the body?
Bones and kidneys
What is the primary source of calcitonin in mammals?
Thyroid gland
In which syndrome is the plasma calcitonin level elevated?
Zollinger–Ellison syndrome
What is the primary function of phosphorylation and dephosphorylation of proteins in the body?
To regulate cell function
Where is the majority of filtered Pi reabsorbed in the kidneys?
Proximal tubule
What happens to NaPi-IIa when it is inhibited by PTH?
It undergoes internalization and degradation
Which process is stimulated by many factors that also increase Ca2+ absorption?
Pi absorption
Which cells are responsible for bone formation?
Osteoblasts
What contributes to the differentiation of osteoblasts?
Extensive growth factor regulation
How do osteoclasts attach to bone?
Via integrins in a sealing zone
What is the function of the periosteum?
Site of ligament attachment
What happens to the cartilage cells at the end of long bone growth during epiphysial closure?
They secrete vascular endothelial growth factor (VEGF)
Which hormone has the most significant impact on the width of the epiphysial plate?
Insulin-like Growth Factor I (IGF-I)
What leads to the closure of the epiphyses in bones?
Hypertrophy of cartilage cells
How is the 'bone age' of a young individual typically determined?
By radiographing the skeleton
Which hormone is responsible for orderly temporal sequence closure of the epiphyses after puberty?
Growth hormone
What is the primary function of the periosteum in relation to bone structure?
Covering and nourishing bone surfaces
How does linear bone growth continue until epiphysial closure?
By new bone formation at the shaft ends
What is the role of Vascular Endothelial Growth Factor (VEGF) in bone development and maturation?
It leads to vascularization and ossification
What is determined by radiographing a young individual's skeleton in relation to bone health?
The 'bone age' based on open or closed epiphyses
Proton pumps acidify the area to approximately pH 7.0.
False
Pyridinolines can be measured in the urine as an index of bone resorption rate.
True
Bone turnover rate is higher in infants than in adults.
True
Bone remodeling involves the deposition of new bone by osteoclasts.
False
Modeling drifts involve changes in bone shapes due to bone resorption and addition in different locations.
True
Osteoblasts break down collagen during bone remodeling.
False
The primary function of pyridinolines is to acidify the bone matrix.
False
Bone resorption rate decreases with age.
False
Bone-remodeling units involve only osteoblasts working in isolation.
False
Osteoclasts resorb bone primarily by forming shallow depressions in the bone.
True
Explore the role of phosphorus in the endocrine system and its connection to calcium & phosphate metabolism. Learn about the importance of phosphorylation and dephosphorylation in regulating cell function. Dive into the total body phosphorus content and its distribution in the body, particularly in the skeleton.
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