The Skeletal System Overview
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Questions and Answers

What is one function of the skeletal system related to mineral storage?

  • Provides energy reserves through adipose tissue
  • Regulates blood sugar levels
  • Stores calcium and phosphorus for bone strength (correct)
  • Produces hormones related to growth

Which type of bone is primarily found in the arms and legs?

  • Long bones (correct)
  • Flat bones
  • Sesamoid bones
  • Irregular bones

Why do humans end up with 206 bones as adults instead of 300 at birth?

  • Some bones are absorbed back into the body
  • Bones fuse together during growth and development (correct)
  • New bones are formed throughout life
  • Some bones are replaced by cartilage

Which type of bone is described as being cube-like in shape?

<p>Short bones (B)</p> Signup and view all the answers

What is a primary characteristic of flat bones?

<p>They are thin and often curved (A)</p> Signup and view all the answers

What is the primary function of long bones in the skeletal system?

<p>Serve as levers for movement (C)</p> Signup and view all the answers

Which bone type serves mainly as points of attachment for muscles?

<p>Flat bones (C)</p> Signup and view all the answers

What type of bones are categorized due to their complex shapes?

<p>Irregular bones (A)</p> Signup and view all the answers

What is the primary function of irregular bones?

<p>Protect internal organs (C)</p> Signup and view all the answers

Which of the following is considered a sesamoid bone?

<p>Patella (B)</p> Signup and view all the answers

What bones comprise the appendicular skeleton?

<p>Pectoral girdle and limb bones (B)</p> Signup and view all the answers

Where is the clavicle located in relation to the axial skeleton?

<p>Articulates with the scapula (A)</p> Signup and view all the answers

Which of these descriptions accurately defines sesamoid bones?

<p>Small round bones found in tendons (C)</p> Signup and view all the answers

What is the role of the pectoral girdle?

<p>Connects limbs to the axial skeleton (D)</p> Signup and view all the answers

How many sesamoid bones are typically found in a person?

<p>Varies significantly from person to person (B)</p> Signup and view all the answers

Which of the following statements about the axial skeleton is correct?

<p>Forms the central axis of the body (D)</p> Signup and view all the answers

What are the two main bones that make up the pectoral girdle?

<p>Clavicle and Scapula (C)</p> Signup and view all the answers

Which part of a long bone is primarily responsible for lengthwise growth during development?

<p>Metaphysis (D)</p> Signup and view all the answers

What is the main function of the articular cartilage found on long bones?

<p>Reduces friction and absorbs shock (D)</p> Signup and view all the answers

Which component of a long bone contains fatty yellow bone marrow?

<p>Diaphysis (C)</p> Signup and view all the answers

What is the purpose of the endosteum in long bones?

<p>Lines the medullary cavity and facilitates growth (D)</p> Signup and view all the answers

Which of the following structures minimizes the weight of the bone while providing maximum strength?

<p>Medullary cavity (A)</p> Signup and view all the answers

Which structure covers the outer surface of a bone?

<p>Periosteum (A)</p> Signup and view all the answers

What is the role of the nutrient foramen in long bones?

<p>Allows blood vessels and nerves to enter the bone (B)</p> Signup and view all the answers

What is the main function of compact bone?

<p>To provide support and protection (B)</p> Signup and view all the answers

Which structural unit is characteristic of compact bone?

<p>Osteon (A)</p> Signup and view all the answers

What distinguishes spongy bone from compact bone?

<p>It contains trabeculae and is lighter (B)</p> Signup and view all the answers

Where does hematopoiesis occur?

<p>Spongy bone (D)</p> Signup and view all the answers

What type of bone typically consists of two layers of compact bone with an interior of spongy bone?

<p>Flat bone (D)</p> Signup and view all the answers

What is the primary characteristic of trabeculae found in spongy bone?

<p>They provide the framework for red marrow (A)</p> Signup and view all the answers

What role does cartilage play in the skeletal system?

<p>It provides cushioning at the ends of long bones (D)</p> Signup and view all the answers

Which type of bone tissue is primarily responsible for strength and density?

<p>Compact bone (C)</p> Signup and view all the answers

What is the function of osteoclasts in bone tissue?

<p>To break down bone tissue (B)</p> Signup and view all the answers

Which cells transform into osteocytes when trapped in the calcified matrix?

<p>Osteoblasts (B)</p> Signup and view all the answers

Where are osteogenic cells primarily located within the bone?

<p>In the periosteum and endosteum (A)</p> Signup and view all the answers

What is the primary role of osteoblasts?

<p>To form new bone (D)</p> Signup and view all the answers

During which process is new bone tissue added?

<p>Bone deposition (C)</p> Signup and view all the answers

What percentage of bone tissue is made up of collagen fibers?

<p>30% (B)</p> Signup and view all the answers

What initiates the transformation of osteogenic cells into osteoblasts?

<p>Differentiation process (A)</p> Signup and view all the answers

Which factor is essential for calcium homeostasis in bone?

<p>Osteoclasts (C)</p> Signup and view all the answers

What is the primary consequence of an imbalance between osteoblasts and osteoclasts?

<p>Bone resorption exceeds bone formation (B)</p> Signup and view all the answers

What effect does resistance training have on bone tissue?

<p>It stimulates increased mineral salt deposition (A)</p> Signup and view all the answers

How does microgravity affect astronauts' bone mass?

<p>Bone loss can be as much as 1% per week (B)</p> Signup and view all the answers

What regulates the release of calcium from bones?

<p>Calcitonin decreases osteoclast activity (A)</p> Signup and view all the answers

What is osteoporosis characterized by?

<p>Faster bone resorption than bone deposition (A)</p> Signup and view all the answers

What happens to an astronaut's bones after returning from a long space mission?

<p>They never fully recover their original structure (C)</p> Signup and view all the answers

What main factor contributes to bone strengthening when exposed to stress?

<p>Increased deposition of mineral salts (A)</p> Signup and view all the answers

Which hormone is responsible for increasing calcium levels in the blood by releasing it from bones?

<p>Parathyroid hormone (D)</p> Signup and view all the answers

Flashcards

Functions of Skeletal System

The skeletal system protects organs, stores minerals, produces blood cells, and provides attachment points for muscles.

Long Bones

Long bones are cylindrical and longer than they are wide; they act as levers for movement.

Short Bones

Short bones are cube-shaped and provide stability and limited motion.

Flat Bones

Flat bones are thin and curved, providing muscle attachment points and protecting internal organs.

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Irregular Bones

Irregular bones have complex shapes and have various functions, depending on the bone.

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Types of Bones

Bones are categorized into long, short, flat, and irregular shapes, each with a specific function.

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Bone Composition

The skeletal system comprises bones, cartilages, and joints, making up 20% of total body mass.

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Number of Bones

A human is born with approximately 300 bones, which fuse during growth to approximately 206 adult bones.

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Sesamoid Bone

A small, round bone, shaped like a sesame seed. Found in tendons and protects them from compressive forces. The patella (kneecap) is the only sesamoid bone in the knee.

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Where are Sesamoid Bones Found?

Sesamoid bones vary in number and placement but are commonly found in tendons associated with the feet, hands, and knees.

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Axial Skeleton

The central axis of the body, including the skull, vertebral column, and thoracic cage.

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Appendicular Skeleton

All the limb bones (arms, legs, hands, and feet) and the bones that connect the limbs to the axial skeleton.

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Pectoral Girdle

The bones that connect each upper limb to the axial skeleton, forming the shoulder girdle.

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What is the clavicle?

The clavicle, or collarbone, is an S-shaped bone on the anterior (front) side of the shoulder. It connects to the sternum and the scapula.

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Pelvic Girdle

The bones that connect the lower limbs to the axial skeleton, forming the hips.

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What is the patella?

The patella, or kneecap, is the only sesamoid bone in the knee. It protects the knee joint and helps smooth out tendon movement.

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Clavicle

The collarbone, a long, S-shaped bone that helps stabilize the shoulder joint and allows movement.

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Scapula

The shoulder blade, a flat, triangular bone that attaches to the clavicle and humerus, allowing for a wide range of arm movements.

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Diaphysis

The long, cylindrical shaft of a long bone. It provides strength and support.

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Epiphyses

The ends of a long bone, responsible for growth and providing points for articulation with other bones.

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Metaphyses

The regions between the diaphysis and epiphyses of a long bone. They contain the growth plates in developing bones.

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Articular Cartilage

A thin layer of cartilage that covers the ends of bones at a joint, reducing friction and acting as a shock absorber.

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Medullary Cavity

The hollow space inside the diaphysis of a long bone containing bone marrow, which produces blood cells.

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Cartilage

Strong, flexible, fibrous tissue found in connective tissues that creates rubber-like padding at the ends of long bones.

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Compact Bone (Cortical Bone)

The denser, stronger type of bone tissue. It provides support and protection, found under the periosteum and in the diaphyses of long bones.

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Spongy Bone (Cancellous Bone)

Lighter type of bone tissue found in the interior of some bones and at the end of long bones. It contains trabeculae and red marrow, where blood cells are produced.

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Osteon

The microscopic structural unit of compact bone, composed of concentric lamellae surrounding a central canal.

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Trabecula

Columns of bone found in spongy bone, creating a network of spaces for red marrow.

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Hematopoiesis

The process of blood cell production, which occurs in the red marrow of some spongy bones.

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What types of bone tissues are found in most bones?

Most bones contain both compact bone and spongy bone tissue, but the distribution and concentration vary based on the bone’s function.

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Give an example of a bone with both compact and spongy bone tissue.

A flat bone consists of two layers of compact bone (outer layers) and an interior layer of spongy bone (inside).

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Bone Tissue Composition

Bone tissue is made up of about 15% water, 30% collagen fibers (for flexibility), and 55% crystallized mineral salts (for hardness and strength). The mineral salts, mainly calcium phosphate and calcium carbonate, combine to form hydroxyapatite crystals.

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Osteogenic Cells

Osteogenic cells are undifferentiated stem cells found in the periosteum and endosteum. They have high mitotic activity and differentiate into osteoblasts.

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Osteoblasts

Osteoblasts are bone-forming cells found in growing bone areas. They synthesize and secrete collagen matrix and calcium salts, contributing to bone deposition.

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Osteocytes

Osteocytes are mature bone cells formed when osteoblasts become trapped within the calcified matrix. They maintain the bone matrix and detect mechanical stress.

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Osteoclasts

Osteoclasts are large, multinucleated cells responsible for breaking down bone (bone resorption). They are essential for calcium homeostasis and found on bone surfaces.

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Bone Remodeling

Bone remodeling is a continuous process involving both bone deposition (new bone formation by osteoblasts) and bone resorption (old bone breakdown by osteoclasts).

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What is Bone Resorption?

Bone resorption is the breakdown of old bone tissue, primarily carried out by osteoclasts. This process releases calcium into the bloodstream and removes damaged bone.

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What is Bone Deposition?

Bone deposition is the process of forming new bone tissue, primarily carried out by osteoblasts. This process involves depositing calcium salts and collagen matrix.

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Calcium Homeostasis

The balance of calcium levels in the blood, maintained by the interaction of hormones and bone tissue.

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Role of Osteoblasts

Osteoblasts are bone-building cells that deposit calcium into bone tissue, increasing bone density and strength.

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Role of Osteoclasts

Osteoclasts are bone-breaking cells that release calcium from bone tissue, contributing to blood calcium levels.

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Impact of Exercise on Bone

Physical activity, especially resistance training, stimulates osteoblasts, leading to increased bone density and strength.

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Microgravity and Bone Loss

Astronauts in space experience bone loss due to reduced gravity, as osteoclast activity is not effectively balanced by osteoblast activity.

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Osteoporosis

A condition characterized by decreased bone density, making bones brittle and prone to fractures.

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Calcium Homeostasis Feedback Loop

A system of hormonal regulation that keeps calcium levels stable in the blood. When calcium levels are low, parathyroid hormone releases calcium from bone; when calcium levels are high, calcitonin decreases calcium release from bone.

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Study Notes

The Skeletal System

  • Comprises bones and cartilage, forming the body's framework.
  • Accounts for approximately 20% of total body weight.
  • A newborn has ~300 bones, but adults have 206.
  • This difference is due to the fusion of some bones during development.

Functions of the Skeletal System

  • Protects internal organs; for instance, rib cage protects lungs and heart, skull protects brain, and spine protects spinal cord.
  • Stores and releases minerals, particularly calcium and phosphorus, contributing to bone strength.
  • Provides a surface for skeletal muscle attachment enabling movement.
  • Produces blood cells in red bone marrow
  • Stores triglycerides (fat) in yellow bone marrow, which serves as an energy source.

Types of Bones

  • Classified into five categories based on shape:
    • Long bones: cylindrical, longer than wide (e.g., femur, humerus, tibia). Function as levers during muscle contraction.
    • Short bones: roughly cube-shaped, approximately equal in length, width, and thickness (e.g., carpals, tarsals). Provide stability and limited movement.
    • Flat bones: thin and often curved (e.g., sternum, ribs, scapulae, cranial bones). Offer muscle attachment points and protect internal organs.
    • Irregular bones: complex shapes (e.g., vertebrae, facial bones). Protect internal organs.
    • Sesamoid bones: small, round bones embedded within tendons (e.g., patella). Protect tendons from compressive forces.

Bone Classifications

  • Summary table describing features, function(s), and example bones for each category.

Axial and Appendicular Skeletons

  • Axial skeleton forms the central axis including skull, vertebral column, and thoracic cage.
  • Appendicular skeleton includes limbs and girdles (shoulder and pelvic).

Pectoral Girdle

  • The clavicle and scapula attach the upper limbs to the axial skeleton.
  • Clavicle connects to the sternum (breastbone) .
  • Lateral end of clavicle articulates with scapula superior to the shoulder joint.

Anatomy of a Long Bone (Diagram)

  • Details of the anatomy: includes the epiphyses, diaphysis, metaphyses, articular cartilage, periosteum, and endosteum.
  • The diaphysis is the long cylindrical portion of the bone.
  • The epiphyses are the expanded ends of the bone.
  • The metaphyses are found between the diaphysis and the epiphyses.
  • The articular cartilage covers the epiphyses where the bone articulates with another bone.
  • The periosteum is a tough outer membrane, covering most of the bone surface.
  • The endosteum lines the medullary cavity.

Bone and Cartilage Differences

  • Bones are rigid connected tissues; cartilage is a flexible connective tissue.
  • Bones are hard, cartilage is soft and elastic.
  • Bones contain blood vessels; cartilage lacks blood vessels.
  • Bones primarily contain calcium phosphates; cartilage does not.

Bone Tissues

  • Compact Bone: Dense, strong, under periosteum and in long bone diaphyses providing support and protection.
  • Spongy Bone: Lighter than compact bone, columns of trabeculae (spaces red marrow). Found in ends of long bones, where hematopoiesis occurs.

Bone Cells

  • Osteogenic cells: undifferentiated cells, located in the endosteum and periosteum, develop into osteoblasts.
  • Osteoblasts: produce bone matrix, and are found in the growing areas of bone, such as periosteum and endosteum, forming collagen and calcium salts.
  • Osteocytes: mature bone cells entrapped in the matrix, maintaining the matrix.
  • Osteoclasts: breakdown bone matrix, found on the surfaces, and are crucial for calcium homeostasis.

Bone Remodeling

  • A dynamic process of constant addition of new bone and removal of old bone.
  • Balance between osteoblasts (building bone) and osteoclasts (breaking down bone) is important.

Bone's Role in Calcium Homeostasis

  • Bones release calcium when levels are low (via osteoclasts) and absorb calcium if levels are high (via osteoblasts).
  • This is regulated by hormones like calcitonin and parathyroid hormone.

Bone Tissue and Exercise

  • Exercises stress bone tissues which results in increased deposition of mineral salts and collagen fibers leading to stronger and denser bones.
  • Resistance training provides greater stimulation than cardiovascular exercises.

Bone Tissue and Microgravity

  • Astronauts in space experience bone loss due to reduced stress from weightlessness on bones.

The Skeletal System and Homeostasis

  • The skeletal system is vital for homeostasis, supporting and protecting organs, storing and releasing calcium.

Osteoporosis

  • A condition resulting from faster bone resorption (breakdown) than deposition (building).
  • Leads to bone mineral density reductions and an increased risk of bone fractures.

Calcium Homeostasis Feedback Loops

  • Controlled by hormones in response to levels of calcium in the blood.

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