Human Anatomy Quiz: Skeletal System

Skeletal System Overview

• The skeletal system is divided into two main parts: the axial skeleton and the appendicular skeleton
• The axial skeleton forms the longitudinal axis of the body and includes the skull, vertebral column, and bony thorax
• The appendicular skeleton includes the limbs (appendages) and the pectoral and pelvic girdles
• The adult human skeleton consists of 206 bones

Skull

• Two sets of bones make up the skull: the cranium and facial bones
• The cranium protects the brain
• Facial bones hold the eyes in place and allow for facial expressions
• Skull bones are joined by sutures (immovable joints)
• The mandible (jawbone) is the only freely movable skull bone

Cranial Bones

• 8 cranial bones
• Frontal bone
• Occipital bone
• 2 Parietal bones
• 2 Temporal bones
• Ethmoid bone
• Sphenoid bone

Facial Bones

• 14 facial bones
• 2 Maxillae
• 2 Palatine bones
• 2 Lacrimal bones
• 2 Zygomatic bones
• 2 Nasal bones
• Vomer bone
• 2 Inferior nasal conchae
• Mandible

Skull Features

• Suture lines join skull bones
• Paranasal sinuses are air-filled cavities within bones that lighten the skull and amplify sounds

Hyoid Bone

• A U-shaped bone in the neck, not directly connected to another bone
• Supports the tongue
• Important for swallowing and speech

Vertebral Column

• Also known as the spine
• Provides axial support that extends from the skull to the pelvis
• Consists of 26 vertebrae separated by intervertebral discs
• Regions include:
  • 7 cervical vertebrae (neck)
  • 12 thoracic vertebrae (chest)
  • 5 lumbar vertebrae (lower back)
  • Sacrum (formed from 5 fused vertebrae)
  • Coccyx (formed from 3-5 fused vertebrae)

Vertebral Column Curvatures

• Primary curvatures (thoracic and sacral regions) are present at birth
• Secondary curvatures (cervical and lumbar regions) develop after birth

Vertebral Structure

• Parts of a typical vertebra include the body, vertebral arch, pedicles, laminae, vertebral foramen, transverse processes, spinous process, and superior and inferior articular processes.

Thoracic Cage

• Protects organs in the thoracic cavity
• Composed of the sternum, ribs, and thoracic vertebrae

Ribs Structure

• True ribs (pairs 1-7), attached directly to sternum
• False ribs (pairs 8-10), attached to cartilage of the 7th rib
• Floating ribs (pairs 11-12), no anterior attachment

Bones of the Appendicular Skeleton

• 126 bones
• Limbs (appendages)
• Pectoral girdle
• Pelvic girdle

Pectoral Girdle

• Composed of the clavicle and scapula
• Provides upper limb attachment to the axial skeleton
• Light, flexible construction allows exceptional mobility

Upper Limbs

• Humerus (arm bone) has proximal and distal articulation points
• Ulna and radius (forearm bones) are both articulate with the humerus.
• Carpals, metacarpals, and phalanges comprise the hand

Pelvic Girdle

• Formed from the fusion of the ilium, ischium, and pubis
• Supports the weight of the upper body
• Protects reproductive organs, bladder, and portion of the large intestine;
• The inlet and outlet of the pelvis differs between the sexes

Lower Limbs

• Femur (thigh bone)
• Tibia and fibula (leg bones)
• Tarsals, metatarsals, and phalanges (foot bones)

Bone Remodeling

• Bones are constantly changing in response to internal and external factors.
• Bone remodeling involves the breakdown of old bone tissue (by osteoclasts) and the formation of new bone tissue (by osteoblasts)
• This process is crucial for maintaining bone integrity and strength
• Also critical for bone repair after a fracture

Bone Fracture

• A fracture occurs when the force applied to a bone exceeds its strength
• Classified as "open" or "closed" depending on whether the broken bone extends through the skin
• Treatment involves reduction (realignment) of bone ends

Fracture Healing

• Bone healing occurs in 4 phases
  • Hematoma formation
  • Fibrocartilage callus formation
  • Bony callus formation
  • Bone remodeling