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Questions and Answers
What is the average number of bones in an adult skeleton?
Which of the following is NOT a part of the axial skeleton?
What type of bone is defined as being located on the midline of the body?
How many vertebrae are found in the cervical region of the vertebral column?
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Which type of muscle is characterized by being involuntary and non-striated?
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Which type of bones are typically found in the wrist?
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What structure protects the spinal cord within the skeletal system?
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Which type of bones contain air-filled spaces and help make the skull lighter?
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The shoulder girdle is formed by which two bones?
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What is one of the key functions of the skeleton?
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Study Notes
Skeletal System
- The skeletal system is composed of bones, cartilage, joints and ligaments
- The average adult skeleton has 206 bones
- Bones can be categorized as paired or unpaired
- A paired bone is two bones of the same type located on the right and left sides of the body, e.g., ribs, hip bone
- An unpaired bone is a bone located on the midline of the body, e.g., sternum
Divisions of the Skeleton
- The axial skeleton includes the skull, vertebral column, ribs and the sternum
- The appendicular skeleton includes the bones of the upper and lower limbs and their girdles
Axial Skeleton
- The skull forms the skeleton of the head and contains two parts:
- Cranium: contains the brain
- Mandible: forms part of facial bones
- The vertebral column is composed of 33 vertebrae and intervertebral discs joining them
- The vertebrae are organized into 5 regions:
- Cervical (7)
- Thoracic (12)
- Lumbar (5)
- Sacral (5 fused, form the sacrum)
- Coccygeal (3-5 fused, form the coccyx)
- The ribs are 12 pairs of ribs with their costal cartilages connecting them to the sternum except for the last 2 ribs (floating ribs)
- The sternum, along with the thoracic vertebrae, the ribs and their costal cartilages form the thoracic cage, containing the heart and lungs
Appendicular Skeleton
- Bones of the upper and lower limbs, plus girdles
- Girdles connect the limbs to the axial skeleton:
- Shoulder (pectoral) girdle
- Pelvic girdle
Bones of the Upper Limb
- Clavicle (Shoulder girdle)
- Scapula (Shoulder girdle)
- Humerus
- Ulna (Medial)
- Radius (Lateral)
- Bones of the hand (Phalanges, metacarpals)
Bones of the Lower Limb
- Hip Bone
- Femur
- Patella
- Tibia & Fibula
- Bones of the foot (Phalanges, metatarsals, tarsals)
Shoulder Girdle
- Formed of clavicle and scapula
- Articulates with the axial skeleton anteriorly via the clavicle
Pelvic Girdle
- Formed by the hip bones
- Articulates with the axial skeleton posteriorly via the sacrum
Bone Classification by Shape
-
Long Bones: (e.g. Femur, Humerus, Radius, Ulna):
- Hard and dense bones
- Provide strength and mobility
- Have a shaft (diaphysis) and two ends (epiphysis)
- Contains a cavity (medullary cavity) that holds bone marrow
-
Short Bones: (e.g., Carpal and Tarsal bones):
- Wide and short bones
- Provide support and stability with little movement
-
Flat Bones: (e.g., Skull cap bones and sternum):
- Protection
- Muscular attachment
-
Irregular Bones: (e.g., Facial bones, vertebrae, and hip bone):
- Unique shapes
- Provide support and protection
-
Pneumatic Bones: (e.g., Some skull bones):
- Contain air-filled spaces
- Make skull lighter, help in resonance of voice
-
Sesamoid Bones: (e.g., Patella)
- Found in tendons
- Protect tendons from excessive wear
Functions of the Skeleton
- Support and movement of the body
- Protection (e.g., the skull protects the brain, the vertebral canal protects the spinal cord, the thoracic cage protects the lungs and heart, the bony pelvis protects the pelvic organs)
- Contain bone marrow
- Storage for salts (e.g., calcium, magnesium)
Muscle Types
-
Skeletal Muscles:
- Striated
- Voluntary
- Responsible for movement
- Attached to bones (or skin)
- Structure: Muscle fibers arranged in bundles
-
Cardiac Muscle:
- Striated
- Involuntary
- Found in the heart
-
Smooth Muscle:
- Non-Striated
- Involuntary
- Found in the wall of viscera (e.g., gastrointestinal tract)
Skeletal Muscles
- Form the main bulk of our bodies (about half of body weight)
- Over 600 muscles in the human body
- A skeletal muscle attaches to bone (or sometimes non-skeletal structures) at two or more places
- Structure: Muscle fibers are arranged in bundles
Muscle Attachments
- Origin: More proximal attachment point of the muscle on a less movable bone
- Insertion: The distal attachment point on the more movable bone
- Action: Describes what happens when the more mobile bone is brought toward the more stable bone during muscular contraction
- Muscle groups for every region of the body:
- Muscles of the head and neck
- Muscles of the trunk
- Muscles of the upper limbs
- Muscles of the lower limbs
Actions of Muscles
- Prime Mover (Agonist): Produces the desired action of a certain movement
- Synergist: Assists the prime mover
- Antagonist: Opposes action of prime mover, restores original position (on the opposite side of the joint)
- Stabilizers: Keep bones immobile when needed
Naming Muscles
- Size: Magnus, major, minor, longus, brevis
- Shape: Deltoid (triangular), teres (cylindrical)
- Orientation of muscle fibers: Rectus, oblique, transverse
- Action of the muscles: Adductor, flexor, extensor, supinator
- Number of heads of a muscle: Bi (two), Tri (three), Quad (four)
- Attachments of the muscle: Sternocmastoid
- Specific Features: Serratus (toothed)
- Location: Abdominis, femoris, pectoralis
Functions of Skeletal Muscles
- Enable humans to move
- Maintain posture
- Generate heat
- Protect organs
- Assist in respiration
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Description
Test your knowledge of the skeletal system, including its components and divisions. Explore the differences between paired and unpaired bones, as well as the structures of the axial and appendicular skeletons. This quiz will assess your understanding of the key features of human bones.
