Bone Matrix Composition and Function

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Questions and Answers

What is the primary substance responsible for the rigidity of bone?

Osteoid

Collagen fibers

Calcium phosphate (correct)

Proteoglycans

Which vitamin is crucial for collagen formation in bones?

Vitamin D

Vitamin B12

Vitamin A

Vitamin C (correct)

What initiates the process of calcification in bone formation?

Presence of osteoblasts

Sufficient calcium and phosphate concentration (correct)

Release of proteolytic enzymes

Absorption of vitamin D

Which component is responsible for the tensile strength of bones?

Collagen Signup and view all the answers

What process involves the destruction of the bone matrix by osteoclasts?

Bone resorption Signup and view all the answers

What is the structure called that is the basic functional and structural unit of compact bone?

Osteon Signup and view all the answers

Which of the following substances enhances calcium absorption from the gastrointestinal tract?

Vitamin D Signup and view all the answers

What happens to bone resorption when blood calcium levels are low?

It increases Signup and view all the answers

What is circumduction?

A continuous sequence of flexion, abduction, extension, and adduction. Signup and view all the answers

What is the primary action of rotation at the atlantoaxial joint?

Pivoting motion of the head. Signup and view all the answers

What occurs during pronation of the forearm?

The palm of the hand is directed posteriorly or inferiorly. Signup and view all the answers

Which movement describes elevation in the context of body movement?

Raising the arms to a superior position. Signup and view all the answers

What does dorsiflexion involve?

Moving the foot's dorsum toward the leg. Signup and view all the answers

Which of the following pairs of movements are considered special movements?

Protraction and retraction. Signup and view all the answers

Which term describes the opposite of supination?

Pronation. Signup and view all the answers

What type of rotation moves the anterior surface of the femur laterally?

Lateral rotation. Signup and view all the answers

What is the primary function of calcitriol as it relates to calcium levels in the body?

Stimulates calcium absorption in the small intestine Signup and view all the answers

How does parathyroid hormone (PTH) affect the conversion of calcidiol to calcitriol in the kidneys?

It increases the rate of conversion. Signup and view all the answers

What type of joint is the elbow joint primarily classified as?

Hinge joint Signup and view all the answers

What synergistic effect do PTH and calcitriol have on the bones?

They increase osteoclast activity, releasing calcium into the blood. Signup and view all the answers

What is the role of calcitonin in regulating blood calcium levels compared to PTH and calcitriol?

Calcitonin plays a minor role in calcium regulation. Signup and view all the answers

Which two articulations make up the elbow joint?

Humeroulnar joint and humeroradial joint Signup and view all the answers

Which organ does not play a significant role in the calcium regulatory actions of calcitriol and PTH?

Liver Signup and view all the answers

What is a key reason for the stability of the elbow joint?

Bony surfaces of the humerus and ulna interlock well. Signup and view all the answers

What role does calcitriol play in the kidneys?

It stimulates calcium reabsorption in the renal tubules. Signup and view all the answers

Which ligament stabilizes the lateral surface of the elbow joint?

Radial collateral ligament Signup and view all the answers

When might the ulnar collateral ligament be torn?

As a result of repetitive use, as observed in baseball pitchers. Signup and view all the answers

What happens to the release of parathyroid hormone (PTH) when blood calcium levels return to normal?

It is inhibited by negative feedback mechanisms. Signup and view all the answers

What is the result of sufficient dietary calcium intake in relation to calcitriol's action on bones?

It can offset calcium loss from bones activated by calcitriol. Signup and view all the answers

What surgical procedure is associated with repairing a torn ulnar collateral ligament?

Tommy John surgery Signup and view all the answers

What role does the anular ligament play in the elbow joint?

It binds the proximal head of the radius to the ulna. Signup and view all the answers

What compromises the mobility of the elbow joint?

The thickness of the articular capsule. Signup and view all the answers

What is the main function of the ligament of head of femur?

It supplies blood to the head of the femur. Signup and view all the answers

Which movements can occur at the hip joint?

Flexion, Extension, Abduction, and Adduction Signup and view all the answers

What structure provides stability to the hip joint?

The bony socket and supporting ligaments Signup and view all the answers

Which joint articulations are included in the knee joint?

The tibiofemoral joint and the patellofemoral joint Signup and view all the answers

Why is the knee classified primarily as a hinge joint?

It only allows flexion and extension. Signup and view all the answers

What is unique about the articular capsule of the knee joint?

It does not cover the anterior surface. Signup and view all the answers

Which of the following statements is NOT true about the knee joint?

It possesses a unified joint cavity. Signup and view all the answers

What happens to the ligaments of the hip joint when the femur is extended?

They become taut and provide stability. Signup and view all the answers

Study Notes

Bone Matrix

Bone is made up of inorganic and organic components that work together for optimal function.
The inorganic portion is primarily calcium phosphate and other salts, forming crystals that give bone its rigidity.
The organic component, osteoid, is made of collagen, proteoglycans, and glycoproteins, providing tensile strength.
A balance of these components is essential: insufficient calcium results in soft bones, while a lack of protein or abnormal protein leads to brittle bones.
Bone formation begins with osteoblasts secreting osteoid, which then calcifies as hydroxyapatite crystals deposit in the bone matrix.
This process requires vitamin D (enhances calcium absorption), vitamin C (collagen formation), calcium, and phosphate.
Bone resorption, the breakdown of bone matrix, is carried out by osteoclasts.
Osteoclasts release proteolytic enzymes and hydrochloric acid (HCl), which break down organic and inorganic components, respectively.
The released calcium and phosphate ions enter the blood.

Compact Bone Microscopic Anatomy

Compact bone is composed of cylindrical structures called osteons, the basic functional and structural units of mature bone.
Osteons are oriented along the long bone's diaphysis and contain a central canal, which carries blood vessels and nerves to supply the bone.
Calcification in the bone matrix requires the presence of hydroxyapatite crystals, formed by the precipitation of calcium and phosphate ions.

Parathyroid Hormone and Calcitriol

Parathyroid hormone (PTH) is secreted by the parathyroid glands in response to low blood calcium levels.
PTH promotes the conversion of calcidiol to calcitriol (active vitamin D3) in the kidneys, increasing the rate of this conversion.
Calcitriol stimulates calcium absorption from the small intestine into the blood, contributing to increased blood calcium levels.
PTH and calcitriol work together to increase calcium release from bone into the blood by promoting osteoclast activity.
Both hormones also act on the kidneys to reduce calcium excretion and increase calcium reabsorption in tubules.

Calcitonin

Calcitonin aids in regulating blood calcium levels, playing a less significant role than PTH or calcitriol.

Rotational Motion

Rotation is a pivoting movement around a bone's longitudinal axis, occurring at joints like the atlantoaxial joint (head rotation).
Lateral rotation (external rotation) turns the anterior surface of a limb laterally, while medial rotation (internal rotation) turns it medially.
Pronation is the medial rotation of the forearm, resulting in the palm facing posteriorly or inferiorly.
Supination is the lateral rotation of the forearm, bringing the palm to face anteriorly or superiorly.

Special Movements

Special movements include depression, elevation, dorsiflexion, plantar flexion, eversion, inversion, protraction, retraction, opposition, and reposition.
Depression involves the inferior movement of a body part (e.g., opening the mouth), while elevation is the superior movement (e.g., closing the mouth).
Dorsiflexion and plantar flexion are limited to the ankle joint, with dorsiflexion moving the toes towards the leg and plantar flexion pointing the toes downwards.

Elbow Joint

The elbow joint is a hinge joint formed by two articulations: the humeroulnar joint (humerus to ulna) and the humeroradial joint (humerus to radius).
It has a thick articular capsule, interlocking bony surfaces, and strong supporting ligaments for stability.
The radial collateral ligament stabilizes the lateral side, while the ulnar collateral ligament strengthens the medial side.
The anular ligament surrounds the head of the radius, supporting its attachment to the ulna.

Hip Joint

The hip joint is a ball-and-socket joint, providing a wide range of motion.
The deep acetabulum, strong articular capsule, supporting ligaments, and muscular padding contribute to its stability.
Movements at the hip include flexion, extension, abduction, adduction, circumduction, and medial/lateral rotation of the femur.

Knee Joint

The knee is the largest and most complex diarthrosis, primarily a hinge joint but capable of some rotation and lateral gliding.
The knee consists of two articulations: the tibiofemoral joint (femur to tibia) and the patellofemoral joint (patella to femur).
The articular capsule encloses the medial, lateral, and posterior regions, but the anterior surface is covered by the quadriceps femoris muscle tendon.
The patella is embedded in this tendon, with the patellar ligament extending to attach to the tibial tuberosity.

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Description

Explore the intricate components that make up the bone matrix, including the balance of inorganic and organic materials essential for bone health. Understand how osteoblasts and osteoclasts play crucial roles in bone formation and resorption. This quiz will test your knowledge on the factors influencing bone strength and the vitamins necessary for optimal bone function.