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What is one primary function of the skeletal system?
Which part of a long bone is responsible for housing the marrow?
Which shape classification does a vertebrae fall under?
What type of bone tissue is primarily found in the ends of long bones?
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In adults, which part of the bone primarily contains red bone marrow?
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What is the primary organic component of bone tissue?
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Which type of bone cell is responsible for the breakdown of bone?
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What is the role of osteocytes in bone tissue?
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Which process involves the transformation of mesenchyme directly into bone?
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What primarily enters the diaphysis of long bones?
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Which component constitutes the majority of the inorganic part of bone?
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What type of bone is produced by endochondral ossification?
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Where are blood and nerves primarily found in bone?
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What is the role of chondrocytes during primary ossification?
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What structure forms over the dead cartilage during primary ossification?
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Where does secondary ossification primarily occur?
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What is the primary function of osteoclasts in bone remodeling?
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What is appositional growth primarily responsible for?
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What characterizes the periosteum layer of bone?
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Which cells are involved in both bone deposition and resorption?
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What is a key requirement for proper bone remodeling?
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Which type of fracture involves damage to the epiphyseal plate and may disrupt bone growth?
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What is the first step in the fracture repair process?
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Which of the following conditions is characterized by excess growth hormone (GH) after closure of growth plates?
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What kind of bone fracture is classified as both complete and open?
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Which of the following disorders is associated with vitamin D deficiency in children?
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What effect does mechanical stress have on osteoblasts?
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Which hormone is responsible for lowering blood calcium levels?
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What is a key role of calcium in the body?
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At what age does the epiphyseal plate typically close for females?
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Which vitamin is necessary for the synthesis of collagen proteins?
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What risk factor for osteoporosis is associated with age?
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Which of the following hormones raises blood calcium levels?
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What lifestyle factor is linked to osteoporosis risk?
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Study Notes
Functions of the Skeletal System
- Support and protect the body
- Enable movement
- Store minerals (calcium and phosphate)
- Participate in blood cell production (red bone marrow)
- Store fat
Divisions of the Skeletal System
- Axial Skeleton: Forms the central axis of the body, including the skull, vertebral column, and rib cage
- Appendicular Skeleton: Consists of the bones of the limbs and their girdles (shoulder and pelvic girdles)
Bone Shapes
- Sutural bones: Small, irregular bones found within sutures (joints) of the skull
- Long bones: Longer than they are wide (e.g., femur, humerus)
- Flat bones: Thin and flattened, often curved (e.g., skull bones, ribs, sternum)
- Short bones: Roughly cube-shaped (e.g., carpals, tarsals)
- Irregular bones: Bones with complex shapes (e.g., vertebrae, facial bones)
- Sesamoid bones: Small round bones embedded in tendons (e.g., patella)
Parts of a Long Bone
- Epiphyses: The expanded ends of a long bone, covered with articular cartilage
- Metaphyses: The regions between the diaphysis and epiphyses, containing the epiphyseal plate/line
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Diaphysis: The shaft or central region of a long bone
- Periosteum: A tough fibrous membrane that surrounds the diaphysis, with collagen fibers that attach it to the bone
- Compact bone: Dense, hard outer layer of the diaphysis
- Endosteum: A thin membranous layer that lines the medullary cavity
- Medullary cavity: The hollow space within the diaphysis, containing bone marrow
Gross Anatomy: Flat/Short Bones
- Compact bone: Outer layer
- Spongy (Cancellous) bone: Inner layer, also known as diploe
- Red bone marrow: Found within spongy bone, responsible for hematopoiesis (blood cell production)
Bone Matrix and Chemistry
- Organic component (33-35%): Primarily collagen fibers, proteoglycans, glycosaminoglycans, glycoproteins, and osteocalcin
- Inorganic component (65-67%): Mainly hydroxyapatite crystals (calcium salts and potassium), along with bicarbonate, magnesium, phosphate, and sodium salts
Blood and Nerves to Bone
- Periosteum: Contains a network of blood vessels and nerves, especially for short, flat, irregular, and sesamoid bones
- Diaphysis: Received blood supply from nutrient arteries entering through the nutrient foramen
- Epiphyses: Supplied by small blood vessels entering through small holes and nutrient arteries
Bone Cells
- Osteoprogenitor cells: Undifferentiated cells give rise to osteoblasts
- Osteoblasts: Bone-building cells, responsible for depositing new bone matrix
- Osteocytes: Mature bone cells, maintain bone matrix
- Osteoclasts: Bone-destroying cells, responsible for bone resorption and remodeling
Bone Production and Resorption
- Osteoblasts: Deposit new bone matrix.
- Osteocytes: Maintain bone.
- Osteoclasts: Breakdown bone matrix to release calcium, contributing to bone remodeling.
Compact Bone Histology
- Consists of osteons (Haversian systems): concentric rings of lamellae (layers) containing osteocytes, surrounding a central canal containing blood vessels and nerves.
- Canaliculi: Tiny channels that connect lacunae (spaces housing osteocytes) and allow for communication and nutrient exchange.
Spongy (Cancellous) Bone Histology
- Composed of trabeculae: interconnected bony plates that form a lattice-like structure.
- Bone marrow: fills spaces within the trabeculae.
Bone Development: 2 Routes
- Intramembranous ossification: Direct formation of bones from mesenchyme, occurs in flat bones (skull, clavicle)
- Endochondral ossification: Replacement of hyaline cartilage by bone, responsible for the formation of long bones.
Intramembranous Ossification
- Primary Ossification: Begins in the center of the bone and moves outwards
- Secondary Ossification: Begins in the epiphyses of long bones, after birth.
Endochondral Ossification
- Hyaline cartilage acts as a template for bone formation.
- Chondrocytes enlarge, calcify, die, and degenerate.
- Perichondrium becomes the periosteum.
Appositional Growth
- Increase in bone diameter
- New bone deposited by osteoblasts in the periosteum and endosteum.
Periosteum and Endosteum
- Periosteum: Outer dense fibrous membrane covering the bone, contains osteoprogenitor cells.
- Endosteum: Thin, inner membranous layer lining bone marrow cavities, contains osteoprogenitor cells.
Bone Remodeling
- Continuous process of bone deposition (by osteoblasts) and resorption (by osteoclasts).
- Ensures bone strength and adaptation to mechanical stress.
- Spongy bone: Replaced by compact bone.
Hormonal Regulation of Bone Growth
- Growth Hormone (GH): Stimulates bone growth.
- Thyroxine (TH): Influences bone growth, working with GH.
- Sex hormones (testosterone and estrogen): Promote bone growth and contribute to the closure of epiphyseal plates.
- Progesterone: Influences bone growth, working with estrogen.
- Calcitonin: Inhibits bone resorption.
- Parathyroid Hormone (PTH): Stimulates bone resorption.
Metabolic Role of Bones
- Calcium: Involved in many bodily functions, including muscle contraction, nerve function, and enzyme activity.
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Hormonal control of blood calcium:
- PTH: Raises blood calcium levels by stimulating bone resorption.
- Calcitonin: Lowers blood calcium levels by inhibiting bone resorption.
Epiphyseal Plate and Line
- Epiphyseal plate: Layer of hyaline cartilage responsible for lengthwise bone growth.
- Epiphyseal line: Forms when the epiphyseal plate closes, marking the end of bone growth.
Vitamins, etc. for Bone Growth
- Calcium: Essential for bone mineralization.
- Vitamin C: Required for collagen synthesis.
- Vitamin D: Aids in calcium absorption and prevents calcium loss through the kidneys.
- Vitamin K: Aids in the production of calcium-binding glycoproteins.
- Protein: Required organic matrix synthesis.
Osteoporosis
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Risk factors:
- Age, genetics (runs in families), gender (female), race, nutrition (low calcium intake, low vitamin D intake, high soda consumption), lack of exercise, certain medications.
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Causes:
- Decreased bone density and weakening of bone tissue, increasing the risk of fractures.
Other Bone Weakening Disorders
- Rickets: A condition caused by vitamin D deficiency in children, resulting in soft and weakened bones.
- Osteomalacia: A condition caused by vitamin D deficiency in adults, resulting in soft and weakened bones.
- Paget's Disease: A condition characterized by abnormal bone remodeling and disorganized bone structure.
Bone Fracture Types
- Incomplete fracture: A crack in the bone that does not completely break it.
- Complete fracture: A bone break that completely severs the bone.
- Displaced fracture: A bone break where the bone fragments are out of alignment.
- Non-displaced fracture: A bone break where the bone fragments remain in alignment.
- Closed (simple) fracture: A bone break that does not break the skin.
- Open (compound) fracture: A bone break that breaks the skin.
Fracture Repair
- Hematoma Formation: Blood clots form at the fracture site.
- Fibrocartilage Callus Formation: Soft callus forms, composed of cartilage and fibrous tissue.
- Bony Callus Formation: Hard callus forms, composed of bone tissue.
- Remodeling: The bony callus is remodeled to resemble the original bone.
Abnormal Growth
- Gigantism: Excessive growth hormone (GH) production, resulting in excessive bone growth.
- Pituitary Dwarfism: Deficiency in GH production, resulting in abnormally short stature.
- Acromegaly: Excessive GH production after epiphyseal plates have closed, causing bone growth in face, hands, and feet.
- Achondroplasia: A genetic disorder characterized by abnormal cartilage growth, resulting in dwarfism.
- Marfan Syndrome: A genetic disorder caused by excessive cartilage growth, leading to long limbs, a tall stature, and other skeletal abnormalities.
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Description
Explore the essential functions and divisions of the skeletal system in this quiz. Learn about the axial and appendicular skeletons, as well as the different shapes of bones in the human body. Test your knowledge on the structural aspects and roles of bones.
