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What are the main minerals stored in bones?
What are the main minerals stored in bones?
Which component of the bone imparts flexible strength to the bone matrix?
Which component of the bone imparts flexible strength to the bone matrix?
Intramembranous ossification is the mode of development in these bones, except:
Intramembranous ossification is the mode of development in these bones, except:
Active bone resorption is a function of which of the following bone cells?
Active bone resorption is a function of which of the following bone cells?
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Blood calcium levels depend on the movement of this mineral in and out of the bone. Levels of calcium in the blood is controlled by?
Blood calcium levels depend on the movement of this mineral in and out of the bone. Levels of calcium in the blood is controlled by?
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What is one of the primary functions of the skeletal system?
What is one of the primary functions of the skeletal system?
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Which structure is primarily responsible for holding bones together?
Which structure is primarily responsible for holding bones together?
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Which part of the skeletal system protects the brain?
Which part of the skeletal system protects the brain?
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Which function of the skeletal system allows the body to maintain upright posture?
Which function of the skeletal system allows the body to maintain upright posture?
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What type of cartilage is known for providing flexibility and is found in structures like the ear?
What type of cartilage is known for providing flexibility and is found in structures like the ear?
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Which component of the skeletal system lies between muscles and bones, providing connectivity?
Which component of the skeletal system lies between muscles and bones, providing connectivity?
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Which element is most directly stored in bones and released as needed for various bodily functions?
Which element is most directly stored in bones and released as needed for various bodily functions?
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What type of growth results in the increase of cartilage size by adding new layers of matrix?
What type of growth results in the increase of cartilage size by adding new layers of matrix?
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In the process of blood cell production, which part of the skeletal system is primarily responsible?
In the process of blood cell production, which part of the skeletal system is primarily responsible?
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What function of the skeletal system is directly achieved by the presence of joints?
What function of the skeletal system is directly achieved by the presence of joints?
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Which cell type is responsible for maintaining the cartilage matrix?
Which cell type is responsible for maintaining the cartilage matrix?
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The ribs protect which of the following organs?
The ribs protect which of the following organs?
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What characteristic does the matrix of cartilage contain to enhance its properties?
What characteristic does the matrix of cartilage contain to enhance its properties?
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What type of growth is characterized by the addition of new matrix at the surface of cartilage by chondroblasts?
What type of growth is characterized by the addition of new matrix at the surface of cartilage by chondroblasts?
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What percentage of the bone matrix is organic constituents, primarily collagen and proteoglycans?
What percentage of the bone matrix is organic constituents, primarily collagen and proteoglycans?
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Which cell type is primarily responsible for bone formation?
Which cell type is primarily responsible for bone formation?
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How do osteocytes primarily communicate with one another?
How do osteocytes primarily communicate with one another?
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What role do osteoclasts play in bone tissue?
What role do osteoclasts play in bone tissue?
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What is the main component of the inorganic part of the bone matrix?
What is the main component of the inorganic part of the bone matrix?
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What initiates the recruitment of osteoclasts during bone remodeling?
What initiates the recruitment of osteoclasts during bone remodeling?
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Which of the following structures is NOT associated with osteocytes?
Which of the following structures is NOT associated with osteocytes?
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What is the function of matrix vesicles secreted by osteoblasts?
What is the function of matrix vesicles secreted by osteoblasts?
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Which cell type is a bone stem cell that can differentiate into bone-forming cells?
Which cell type is a bone stem cell that can differentiate into bone-forming cells?
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What is the primary method by which long bones increase in length?
What is the primary method by which long bones increase in length?
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Which of the following hormones is primarily responsible for stimulating interstitial cartilage growth?
Which of the following hormones is primarily responsible for stimulating interstitial cartilage growth?
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What are osteoclasts primarily responsible for in the context of calcium homeostasis?
What are osteoclasts primarily responsible for in the context of calcium homeostasis?
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What condition results from a deficiency of vitamin D in childhood?
What condition results from a deficiency of vitamin D in childhood?
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At what age does the closure of the epiphyseal plate typically occur, marking the cessation of growth in length for long bones?
At what age does the closure of the epiphyseal plate typically occur, marking the cessation of growth in length for long bones?
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What is the primary role of osteoclasts in bone physiology?
What is the primary role of osteoclasts in bone physiology?
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Which type of bone is characterized by collagen fibers that are randomly oriented?
Which type of bone is characterized by collagen fibers that are randomly oriented?
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What structure is associated with spongy bone?
What structure is associated with spongy bone?
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Which of the following is true regarding compact bone compared to spongy bone?
Which of the following is true regarding compact bone compared to spongy bone?
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What features characterize an osteon?
What features characterize an osteon?
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What are canaliculi primarily responsible for in compact bone?
What are canaliculi primarily responsible for in compact bone?
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Which type of lamellae forms the outer surfaces of compact bone?
Which type of lamellae forms the outer surfaces of compact bone?
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What occurs during the differentiation of osteoclast plasma membranes?
What occurs during the differentiation of osteoclast plasma membranes?
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Which statements correctly describe lamellar bone?
Which statements correctly describe lamellar bone?
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How do perforating (Volkmann) canals contribute to the overall function of the bone?
How do perforating (Volkmann) canals contribute to the overall function of the bone?
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Which function of the skeletal system primarily aids in the body's movement?
Which function of the skeletal system primarily aids in the body's movement?
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What is the role of hydroxyapatite in bone structure?
What is the role of hydroxyapatite in bone structure?
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What role do ligaments play in the skeletal system?
What role do ligaments play in the skeletal system?
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Which of the following is a characteristic of the skeletal system's role in calcium homeostasis?
Which of the following is a characteristic of the skeletal system's role in calcium homeostasis?
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How do osteoblasts contribute to bone physiology?
How do osteoblasts contribute to bone physiology?
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What is the primary component of bone that aids in its resilient structure?
What is the primary component of bone that aids in its resilient structure?
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What condition is caused by a lack of adequate vitamin D during childhood?
What condition is caused by a lack of adequate vitamin D during childhood?
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Which type of bone is essential for bearing weight and providing structural integrity during movement?
Which type of bone is essential for bearing weight and providing structural integrity during movement?
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What is the key feature of intramembranous ossification compared to endochondral ossification?
What is the key feature of intramembranous ossification compared to endochondral ossification?
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Which hormone is primarily involved in increasing blood calcium levels?
Which hormone is primarily involved in increasing blood calcium levels?
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At what point does the closure of the epiphyseal plate typically occur?
At what point does the closure of the epiphyseal plate typically occur?
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Which vitamin deficiency is associated with osteomalacia in adults?
Which vitamin deficiency is associated with osteomalacia in adults?
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What process describes the replacement of old bone with new bone tissue?
What process describes the replacement of old bone with new bone tissue?
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What is the primary role of chondrocytes in cartilage?
What is the primary role of chondrocytes in cartilage?
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Which type of cartilage is known for providing strength and is often found in intervertebral discs?
Which type of cartilage is known for providing strength and is often found in intervertebral discs?
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What function does the perichondrium serve in the skeletal system?
What function does the perichondrium serve in the skeletal system?
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What are the primary functions of tendons in the skeletal system?
What are the primary functions of tendons in the skeletal system?
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Which component of the skeletal system is primarily responsible for blood cell production?
Which component of the skeletal system is primarily responsible for blood cell production?
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What is one way that bones act as a storage system in the body?
What is one way that bones act as a storage system in the body?
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What do ligaments do in relation to skeletal function?
What do ligaments do in relation to skeletal function?
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What types of cartilage are primarily found in the skeletal system?
What types of cartilage are primarily found in the skeletal system?
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What benefits does the matrix of cartilage provide?
What benefits does the matrix of cartilage provide?
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Which of these components is NOT considered part of the skeletal system?
Which of these components is NOT considered part of the skeletal system?
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What structural characteristic differentiates lamellar bone from woven bone?
What structural characteristic differentiates lamellar bone from woven bone?
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Which structure is primarily associated with spongy bone?
Which structure is primarily associated with spongy bone?
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What is the primary role of the ruffled border in osteoclasts?
What is the primary role of the ruffled border in osteoclasts?
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Which type of bone contains more bone matrix and less space?
Which type of bone contains more bone matrix and less space?
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Which of the following statements is true regarding the organization of osteocytes in lamellar bone?
Which of the following statements is true regarding the organization of osteocytes in lamellar bone?
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Which structure does NOT play a role in connecting osteons?
Which structure does NOT play a role in connecting osteons?
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What do canaliculi facilitate in bone tissue?
What do canaliculi facilitate in bone tissue?
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What type of lamellae forms the outer surface of compact bone?
What type of lamellae forms the outer surface of compact bone?
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What defines an osteon in compact bone?
What defines an osteon in compact bone?
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What defines the process of ossification in bone tissue?
What defines the process of ossification in bone tissue?
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What role do osteocytes play in bone maintenance?
What role do osteocytes play in bone maintenance?
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What is the primary component of the inorganic matrix of bone?
What is the primary component of the inorganic matrix of bone?
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Which statement correctly describes osteoclasts?
Which statement correctly describes osteoclasts?
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Which cellular structure allows osteocytes to obtain nutrients?
Which cellular structure allows osteocytes to obtain nutrients?
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What initiates the process of bone remodeling?
What initiates the process of bone remodeling?
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Which part of the bone is responsible for secretion of matrix vesicles?
Which part of the bone is responsible for secretion of matrix vesicles?
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What is the primary role of osteoprogenitor cells?
What is the primary role of osteoprogenitor cells?
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Which feature of osteoclasts enhances their ability to absorb bone tissue?
Which feature of osteoclasts enhances their ability to absorb bone tissue?
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In which location can osteochondral progenitor cells be found?
In which location can osteochondral progenitor cells be found?
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Study Notes
Skeletal System Functions
- Provide support and protection for the body
- Enable body movement by facilitating the attachment of muscles to bones
- Store calcium and phosphorus, which are essential for various bodily functions
- Produce blood cells, which are essential for oxygen transport and immune function
Components of the Skeletal System
- Bone: Hard and rigid tissue that provides support and protection.
-
Cartilage: Firm and flexible tissue that cushions joints, supports the shape of the nose and ears, and provides the framework for developing bones.
- Types: Hyaline, Fibrocartilage, Elastic cartilage.
- Cells: Chondroblasts and Chondrocytes.
- Ligaments: Connective tissue that connects bones to each other and help stabilize joints.
- Tendons: Connective tissue that connects muscles to bones, enabling muscle to move the skeleton.
Bone Histology
-
Bone Matrix: The extracellular material that surrounds bone cells.
- Organic (35%): Collagen and proteoglycans for tensile strength and flexibility.
- Inorganic (65%): Hydroxyapatite (calcium phosphate crystals) for hardness and rigidity.
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Bone Cells:
- Osteochondral Progenitor Cells: Undifferentiated bone stem cells.
- Osteoblasts: Bone-building cells that synthesize and secrete bone matrix.
- Osteocytes: Mature bone cells that maintain the bone matrix and help regulate calcium homeostasis.
- Osteoclasts: Bone-resorbing cells that break down bone tissue.
Bone Types
- Woven Bone: Collagen fibers are randomly oriented, found in developing bones and fracture sites, weaker than compact bone.
- Lamellar Bone: Stronger type of bone with collagen fibers arranged in parallel sheets (lamellae), found in mature bones.
- Spongy Bone: Lighter type of bone with a porous structure, contains trabeculae (interconnected bony plates) filled with bone marrow.
- Compact Bone: Dense and solid bone that forms the outer layer of bones, contains osteons (functional units of compact bone) with central canals containing blood vessels.
Bone Development
- Intramembranous Ossification: Formation of bone directly from mesenchymal tissue (connective tissue), occurs in skull bones, part of the mandible, and clavicle.
- Endochondral Ossification: Formation of bone from cartilage, occurs in most bones, including long bones and the base of the skull.
Bone Growth
- Growth in Length: Occurs at the epiphyseal plate (growth plate) of long bones, involves endochondral ossification, and ends with the closure of the epiphyseal plate, marking the end of long-bone growth.
- Growth in Width: Occurs through appositional growth, involves the deposition of new bone tissue by osteoblasts beneath the periosteum, contributing to bone thickness and circumference.
Factors Affecting Bone Growth
-
Nutrition:
- Vitamin D: Essential for calcium absorption from the intestines, deficiency leads to rickets (children) or osteomalacia (adults).
- Vitamin C: Necessary for collagen synthesis, deficiency leads to scurvy.
-
Hormones:
- Growth Hormone (GH): Promotes bone growth, especially at the epiphyseal plate, deficiency leads to dwarfism, excess leads to gigantism.
- Thyroid Hormone: Required for normal bone growth and development.
- Reproductive Hormones (Estrogen and Testosterone): Promote bone growth during puberty, eventually lead to closure of the epiphyseal plate and cessation of long-bone growth.
Calcium Homeostasis
- Bone: Serves as the major storage site for calcium.
- Blood Calcium Levels: Regulated by the movement of calcium in and out of bone.
-
Hormones:
- Parathyroid Hormone (PTH): Increases blood calcium levels by stimulating osteoclast activity, promoting calcium reabsorption in the kidneys, and indirectly promoting the activation of calcitriol (a hormone that increases calcium absorption from the intestines).
- Calcitriol (Vitamin D3): Increases calcium absorption in the intestines.
- Calcitonin: Lowers blood calcium levels by inhibiting osteoclast activity.
Bone Remodeling
- Continuous process of replacing old bone with new bone tissue involving both bone resorption by osteoclasts and bone formation by osteoblasts.
- Essential for bone growth, shaping, repair, adaptation to stress, and maintaining calcium homeostasis.
- Basic Multicellular Unit (BMU): Functional unit of bone remodeling, composed of osteoclasts and osteoblasts working together, responsible for the continuous renewal of the skeleton, estimated to replace the entire skeleton every 10 years.
The Skeletal System
- The skeletal system is a vital structure that provides numerous functions including:
- Support
- Protection
- Movement
- Storage
- Blood cell production
- It is comprised of four main components:
- Bone
- Cartilage
- Tendons
- Ligaments
Cartilage
- Cartilage is a type of connective tissue that supports and protects joints.
- It is composed of three types:
- Hyaline cartilage
- Fibrocartilage
- Elastic cartilage
- The cells within cartilage are called chondrocytes, which are responsible for maintaining the cartilage matrix.
- Chondroblasts are responsible for forming new cartilage matrix.
- Cartilage growth can occur through two processes:
- Appositional growth, where new matrix is added to the existing cartilage from the perichondrium.
- Interstitial growth, where chondrocytes divide and produce additional matrix within the existing cartilage.
Bone
- Bone is made of a matrix composed of organic material (collagen and proteoglycans) and inorganic material (hydroxyapatite).
- Bone cells include:
-
Osteochondral progenitor cells:
- Bone stem cells derived from mesenchymal cells.
- Found in the inner portion of periosteum, endosteum, and perichondrium.
- Can undergo cell division.
-
Osteoblasts:
- Bone-building cells.
- Derived from osteochondral progenitor cells.
- Secrete collagen and proteoglycans.
- Secrete matrix vesicles containing high concentrations of calcium and phosphate.
-
Osteocytes:
- Mature bone cells.
- Relatively inactive, but can still produce small amounts of matrix.
- Connected to each other through canaliculi.
- Get nutrients through the canaliculi, lacunae, and gap junctions.
-
Osteoclasts:
- Bone-destroying cells
- Massive, multinucleated cells.
- Derived from monocyte/macrophage lineage stem cells.
- Have a ruffled border, which is the main site of bone resorption.
-
Osteochondral progenitor cells:
- The process of bone formation is called ossification.
- Intramembranous ossification begins with connective tissue membranes during embryonic development, and forms many skull bones, parts of the clavicle and mandible.
- Endochondral ossification starts with a cartilage model, and forms the base of the skull, parts of the clavicle and mandible, and most of the remaining skeleton.
Bone Growth
-
Growth in length:
- Occurs at the epiphyseal plate, a region of cartilage growth between the diaphysis and epiphysis of long bones.
- The process involves endochondral ossification, where interstitial cartilage growth is followed by appositional bone growth.
- The epiphyseal plate closes during late adolescence or early adulthood, forming the epiphyseal line.
-
Growth in width:
- Occurs at the periosteum, the outer layer of the bone.
Bone Remodeling
- Bone remodeling is a continuous process where old bone is replaced with new bone.
- This process is essential for:
- Converting woven bone into lamellar bone.
- Supporting bone growth and repair.
- Adjusting bone shape in response to stress.
- Maintaining calcium homeostasis.
- It is performed by a functional unit called the Basic Multicellular Unit (BMU), which is made up of coordinated osteoclasts and osteoblasts.
- The entire skeleton is renewed approximately every 10 years.
Calcium Homeostasis
- Bone is a primary storage site for calcium.
- Blood calcium levels are controlled by three main hormones:
-
Parathyroid hormone (PTH):
- Released by the parathyroid gland when blood calcium levels decrease.
- Increases blood calcium levels by stimulating osteoclast activity, increasing calcium reabsorption in the kidneys, and promoting calcitriol activation in the intestines.
-
Calcitriol (vitamin D3):
- Increases blood calcium levels by increasing intestinal absorption of calcium.
-
Calcitonin:
- Released by the thyroid gland when blood calcium levels are high.
- Decreases blood calcium levels by inhibiting osteoclast activity.
-
Parathyroid hormone (PTH):
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Description
Explore the essential functions of the skeletal system, including support, protection, and movement facilitation. Learn about the various components such as bones, cartilage, ligaments, and tendons, and understand their roles in maintaining the body's structure and function.
