Human Skeletal System Overview

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Questions and Answers

What is the role of hyaline cartilage in the skeletal system?

Provides rigidity and strength

Facilitates blood flow

Absorbs shock during movement

Provides support, flexibility, and resilience (correct)

How many bones comprise the adult human skeleton?

214

206 (correct)

202

210

Which statement about skeletal cartilages is true?

They contain no blood vessels or nerves. (correct)

They contain many blood vessels and nerves.

They are primarily composed of elastic fibers.

They directly connect bones to muscles.

What are the two categories of bones in the human skeleton?

Axial and appendicular skeletons Signup and view all the answers

At what age does the human skeleton typically cease growth?

25 years Signup and view all the answers

What process describes the growth of cartilage where cells secrete matrix against the external face?

Appositional growth Signup and view all the answers

Which of the following is NOT a component of the axial skeleton?

Pelvis Signup and view all the answers

What type of cartilage is primarily found in the intervertebral discs?

Fibrocartilage Signup and view all the answers

What is the main role of the axial skeleton?

Protect vital organs Signup and view all the answers

Which cartilage type is characterized by a dense arrangement of collagen fibers and is found in joints?

Fibrocartilage Signup and view all the answers

What happens to cartilage during normal bone growth?

It calcifies Signup and view all the answers

Which statement about the appendicular skeleton is false?

It supports vital organs. Signup and view all the answers

What is the primary component of the costal cartilage?

Hyaline cartilage Signup and view all the answers

Which type of bone is primarily found in the limbs and clavicle?

Long bones Signup and view all the answers

What is a major function of bones in the human body?

Support and protection Signup and view all the answers

Which type of bone is defined as having a cube-like shape?

Short bones Signup and view all the answers

What term describes the rounded projection on a bone that serves as a site of muscle attachment?

Tuberosity Signup and view all the answers

What are trabeculae in spongy bone responsible for?

Providing structural integrity Signup and view all the answers

In the context of bone structure, what is the diaphysis?

The shaft or long part of a bone Signup and view all the answers

What is the role of osteoclasts in bone physiology?

They break down bone tissue Signup and view all the answers

What is the primary mineral responsible for the hardness of bone?

Calcium phosphate Signup and view all the answers

Which hormone increases calcium levels by stimulating osteoclast activity?

Parathyroid hormone Signup and view all the answers

What is the function of the periosteum?

To cover and protect bones Signup and view all the answers

What type of bone marking is characterized by a narrow ridge of bone?

Crest Signup and view all the answers

What is the main purpose of spongy bone?

Reduce weight of bones Signup and view all the answers

Which classification of bones is primarily found providing protection or muscular attachment?

Flat bones Signup and view all the answers

What is the significance of the Haversian system in compact bone?

Facilitates nutrient and waste exchange Signup and view all the answers

Study Notes

Introduction

The human skeleton is initially composed of cartilage and fibrous membranes.
Hyaline cartilage is the most common type of cartilage.
The skeleton is completely ossified (hardened) by age 25 and growth ceases.
The adult skeleton is composed of 206 bones, making up about 20% of body mass. Axial skeleton comprises 80 bones, while the appendicular skeleton holds 126 bones.

Skeletal System

The skeletal system is a network of bones, ligaments, and tendons.
It provides body support and protects internal organs.
It consists of 206 bones.

Skeletal Cartilages

Cartilage lacks blood vessels and nerves.
It is a dense connective tissue with a perichondrium, which contains blood vessels that supply nutrients to the cartilage.

Types of Skeletal Cartilages

Hyaline cartilage is the most abundant type, offering support, flexibility, and resilience.
Elastic cartilage is similar to hyaline cartilage but contains elastic fibers.
Fibrocartilages are strong and tough, able to withstand heavy pressure.

Growth of Cartilage

Appositional growth involves cells secreting matrix against the existing cartilage's external face.
Interstitial growth occurs when chondrocytes divide and secrete new matrix within the cartilage, expanding it.
Calcification of cartilage happens during normal bone growth and aging.

Bones of the Skeleton

The skeletal system is divided into two groups based on location:
- Axial skeleton: Includes the skull, vertebrae, and rib cage (blue in the example image).
- Appendicular skeleton: Includes the bones of the limbs, shoulder girdle, and pelvic girdle (pink in the example image).

Divisions of the Skeletal System

Axial skeleton: The central skeleton protecting and supporting vital organs.
Appendicular skeleton: Skeleton of the limbs.

Axial Skeleton

Made of the skull and vertebrae.
Primarily flat and irregular bones.
Protects organs like the brain, heart, and lungs.
Supports the body along the central axis (backbone).

Parts of the Axial Skeleton

Skull: Protects the brain.
Vertebrae: Protects the spinal cord and keeps the skeleton upright.
Ribs: Protect the lungs and heart, providing a surface for intercostal muscles during breathing.

Appendicular Skeleton

Consists of the bones of the limbs, shoulder girdle, and pelvic girdle.
Essential for load transfer in the body.

Classification of Bones by Shape

Long bones: Bones that are longer than they are wide.
Short bones: Cubical-shaped bones found in wrists and ankles. Sesamoid bones, like the patella, are found within tendons.
Flat bones: Thin, flat, and slightly curved bones.
Irregular bones: Complicated shaped bones.

Long Bones

Located in the limbs and clavicle.
Each bone has a shaft (diaphysis) and two ends (epiphyses).
The wall comprises dense tissue.
The central canal, called the medullary canal, contains bone marrow.

Short Bones

Found in areas requiring strength, compactness, and limited movement.
Key examples: Tarsus (7 bones in the foot) and Carpus (8 bones in the wrist).

Flat Bones

Found where protection or muscular attachment is needed.
Primarily located in the skull and scapula.
Found in the ribs.

Irregular Bones

Bones with shapes that don't fit into other categories.
Examples: Vertebrae, sphenoid, and hyoid.

Functions of Bones

Support: For the body and soft organs.
Protection: For the brain, spinal cord, and vital organs.
Movement: Act as levers for muscle action.
Mineral Storage: Store essential minerals like calcium and phosphorus, as well as growth factors.
Blood Cell Formation (Hematopoiesis): Occurs in bone marrow cavities.
Triglyceride Storage: Stored in bone cavities for energy reserves.

Bone Markings

Bulges, depressions, and holes on bones serve specific functions.
Sites of attachment for muscles, ligaments, and tendons.
Joint surfaces.
Conduits for blood vessels and nerves.

Projections for Muscle and Ligament Attachment

Tuberosity: Rounded projection.
Crest: Narrow, prominent ridge.
Trochanter: Large, blunt, irregular surface.
Line: Narrow ridge of bone.
Tubercle: Small rounded projection.
Epicondyle: Raised area above a condyle.
Spine: Sharp, slender projection.
Process: Any bony prominence.

Projections for Joint Formation

Head: Bony expansion carried on a narrow neck.
Facet: Smooth, nearly flat articular surface.
Condyle: Rounded articular projection.
Ramus: Armlike bar.

Depressions and Openings

Meatus: Canal-like passageway.
Groove: Furrow.
Sinus: Cavity within a bone.
Fissure: Narrow, slitlike opening.
Fossa: Shallow, basinlike depression.
Foramen: Round or oval opening through a bone.

Bone Textures

Compact bone: Dense outer layer.
Spongy (cancellous) bone: Honeycomb-like structure with trabeculae.

Structure of a Long Bone

Diaphysis (shaft): Compact bone collar enclosing the medullary (marrow) cavity.
Medullary cavity: Contains fat (yellow marrow) in adults.

Structure of a Long Bone (Continued)

Epiphyses (expanded ends): Spongy bone interior.
Epiphyseal line: A remnant of the growth plate.
Articular (hyaline) cartilage: Covers the joint surfaces.

Membranes of Bone

Periosteum: Double-layered membrane.
- Outer fibrous layer: Connective tissue layer.
- Inner osteogenic layer: Contains osteoblasts, osteoclasts, and osteogenic cells (stem cells).
- Nerves, blood vessels, and lymphatic vessels enter the bone through nutrient foramina. Secured to the underlying bone by Sharpey's fibers.

Membranes of Bone (Continued)

Endosteum: A delicate membrane lining the internal surfaces of the bone. Contains osteogenic cells, osteoblasts, and osteoclasts.

Structure of Short, Irregular, and Flat Bones

Periosteum-covered compact bone: On the outside.
Endosteum-covered spongy bone: Within the bone.
Spongy bone called diploë: In flat bones.
Bone marrow: Between the trabeculae.

Location of Hematopoietic tissue (Red Marrow)

Adults: Trabecular cavities of the heads of femur and humerus, trabecular cavities of diploë in flat bones.
Newborn infants: Medullary cavities and all spaces in spongy bone.

Microscopic Anatomy of Bone: Cells

Osteogenic (osteoprogenitor) cells: Stem cells in periosteum and endosteum that give rise to osteoblasts.
Osteoblasts: Bone-forming cells that secrete osteoid.
Osteocytes: Mature bone cells that maintain bone matrix.
Osteoclasts: Cells that break down (resorb) bone matrix.

Microscopic Anatomy of Bone: Compact Bone

Haversian system (osteon): Structural unit of the bone.
- Lamellae: Concentric rings of matrix tubes that bear weight.
- Central (Haversian) canal: Contains blood vessels and nerves.

Microscopic Anatomy of Bone: Compact Bone (Continued)

Perforating (Volkmann’s) canals: Channels perpendicular to central canal for blood vessels and nerves.
Lacunae: Small cavities containing osteocytes.
Canaliculi: Tiny canals connecting lacunae to each other and central canal.

Microscopic Anatomy of Bone: Spongy Bone

Trabeculae: Aligned along lines of stress, lacking osteons.
Contains irregularly arranged lamellae, osteocytes, and canaliculi.
Capillaries in the endosteum provide nutrients.

Chemical Composition of Bone: Organic

Cells: Osteogenic, osteoblasts, osteocytes, and osteoclasts.
Osteoid: Organic bone matrix secreted by osteoblasts. Contains ground substance (proteoglycans, glycoproteins) and collagen fibers.

Chemical Composition of Bone: Inorganic

Hydroxyapatites (mineral salts): 65% of bone by mass, mainly calcium phosphate crystals.
Contribute to hardness and resistance to compression.

Factors Affecting Bone Growth and Development

Nutrition: Mainly calcium consumption, along with other nutrients vital for bone health.
Exposure to Sunlight: Essential for Vitamin D production, which facilitates calcium absorption in the small intestine.
Hormonal Secretion: Human growth hormone (somatotropin) stimulate activity in the epiphyseal plate.
Physical Exercise: Promotes increased bone density and strength.

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Description

This quiz covers the basics of the human skeletal system, including its composition, structure, and types of cartilage. Understand the differences between the axial and appendicular skeleton, as well as the significance of various types of skeletal cartilages. Dive into the fascinating world of bones and connective tissues.