Essentials of Human Anatomy and Physiology

Essentials of Human Anatomy and Physiology

5.3 The Skeletal System Overview

  • The skeletal system consists of bones, joints, cartilage, and ligaments, which provides support, movement, and protection for body organs.

5.3a Bones of the Shoulder Girdle

  • The pectoral girdle (shoulder girdle) consists of two bones: the clavicle and the scapula.

    • Clavicle (Collarbone)

      • Description: Slender, doubly curved bones.

      • Connection: Attaches medially to the manubrium of the sternum at its sternal end and laterally to the scapula, forming part of the shoulder joint.

      • Function: Holds the arm away from the thorax and prevents shoulder dislocation. Damage to the clavicle can cause the shoulder region to cave in.

    • Scapula (Shoulder Blade)

      • Description: Known as "wings" due to their flaring motion.

      • Attachment: Not directly attached to the axial skeleton, loosely held by trunk muscles.

      • Anatomy: Each scapula has a triangular shape with three borders (superior, medial (vertebral), lateral (axillary)) and three angles (superior, inferior, lateral).

      • Glenoid Cavity: A shallow socket in the lateral angle that receives the head of the arm bone.

      • Processes:

      • Acromion: Enlarged lateral end of the scapula spine, connects with the clavicle at the acromioclavicular joint.

      • Coracoid Process: Beaklike process that anchors muscles and points laterally over the shoulder.

      • Suprascapular Notch: A nerve passageway located just medial to the coracoid process.

      • Flexibility & Dislocation Risk:

      • The shoulder girdle's lightness and loose attachment to the thorax permits exceptional movement but increases susceptibility to dislocation.

5.3b Bones of the Upper Limbs

  • Each upper limb has 30 separate bones including the arm, forearm, and hand.

Arm

  • The arm consists of a single bone: the Humerus.

    • Anatomy & Features:

      • Proximal End: Rounded head fits into the glenoid cavity of the scapula.

      • Anatomical Neck: Slight constriction below the head.

      • Tubercles: Greater and lesser tubercles serve as muscle attachment sites.

      • Surgical Neck: Common site of fractures.

      • Deltoid Tuberosity: Roughened area for attachment of the deltoid muscle.

      • Radial Groove: Marks the course of the radial nerve.

      • Distal Ends: Includes medial trochlea (spool-like shape) and lateral capitulum (ball-like shape) which articulate with forearm bones.

      • Depressions: Coronoid fossa (anterior) and olecranon fossa (posterior) allow elbow movement.

Forearm

  • The forearm consists of two bones: Radius and Ulna.

    • Radius:

      • Lateral bone in the anatomical position (thumb side).

      • Forms joint with the capitulum of the humerus.

      • Has a styloid process at the distal end and a radial tuberosity for biceps muscle attachment.

    • Ulna:

      • Medial bone (little finger side) in the anatomical position.

      • Proximal end features the coronoid and olecranon processes, separated by the trochlear notch for joint action with the humerus.

Hand

  • The hand's skeleton consists of three types of bones:

    • Carpals: 8 bones arranged in two irregular rows of four each, forming the carpus (wrist).

      • Function: Bound together by ligaments that restrict movement.

    • Metacarpals: 5 bones forming the palm, numbered 1 (thumb) to 5 (little finger).

      • Function: Their heads become knuckles when the fist is clenched.

    • Phalanges: Bones of the fingers; each hand contains 14 phalanges (3 in each finger - proximal, middle, distal; 2 in the thumb - proximal, distal).

Exam Questions

  1. Contrast the general function of the axial skeleton to that of the appendicular skeleton.

  1. What is the single point of attachment of the shoulder girdle to the axial skeleton?

  1. What bone forms the skeleton of the arm?

  1. Where are the carpals found, and what type of bone are they?

  1. Which bones of the upper limb have a styloid process?

For answers, refer to Appendix A.

The Skeletal System Overview

The Arm and Forearm Bones

  • Bones of the Arm

    • Humerus

    • Greater tubercle

    • Lesser tubercle

    • Head of humerus

    • Anatomical neck

    • Intertubercular sulcus

    • Surgical neck

    • Deltoid tuberosity

    • Radial groove

    • Radial fossa

    • Medial epicondyle

    • Olecranon fossa

    • Coronoid fossa

    • Capitulum

    • Trochlea

  • Bones of the Forearm

    • Radius

    • Radial tuberosity

    • Distal ulnar styloid process

    • Ulna

    • Olecranon

    • Coronoid process

    • Proximal radioulnar joint

    • Interosseous membrane

Pelvic Girdle Anatomy

  • Definition: The pelvic girdle, or hips, is comprised of two coxal bones and the sacrum.

  • Components:

    • Coxal Bones (Hip Bones): Each formed by the fusion of three bones:

    • Ilium

      • Connects with the sacrum at the sacroiliac joint

      • Forms most of the hip bone, referred to as "alae"

      • Iliac crest is an important landmark for injections

      • Anterior superior iliac spine and posterior superior iliac spine are located at the edges of the iliac crest

      • Greater sciatic notch allows passage of blood vessels and nerves

    • Ischium

      • Known as the "sit-down bone"

      • Ischial tuberosity supports body weight when sitting

      • Ischial spine is significant during childbirth as it narrows the pelvic outlet

    • Pubis

      • The most anterior and inferior part

      • Forms a joint known as the pubic symphysis

      • Surrounds the obturator foramen for vessel and nerve passage

  • Acetabulum: Deep socket in the pelvic girdle that receives the head of the femur.

Differentiation of Male and Female Pelvis

  • Pelvic Division:

    • False Pelvis: Superior to true pelvis

    • True Pelvis: Surrounded by bone, critical for childbirth

  • Key Differences between Male and Female Pelvis:

    • Female inlet is larger and circular

    • Female pelvis is shallower; bones lighter and thinner

    • Female ilia flare more laterally

    • Female sacrum is shorter and less curved

    • Female ischial spines are shorter and farther apart

    • Female pubic arch has a greater angle, rounded shape

The Lower Limbs

  • Segments of Lower Limbs: Thigh, leg, foot

    • Thigh:

    • Femur:

      • Heaviest and strongest bone, longest in the body

      • Proximal features: head, neck, greater and lesser trochanters, intertrochanteric line/crest, gluteal tuberosity

      • Articulates at acetabulum with the hip bone

      • Medially slants to align knees with body center of gravity

      • Distal features: medial and lateral condyles articulating with tibia

      • Intercondylar fossa separates the condyles

      • Patellar surface for articulation with patella

    • Leg:

    • Composed of Tibia and Fibula

      • Tibia is larger, medial, and forms knee joint with femur

      • Has medial condyle, lateral condyle, intercondylar eminence

      • Distal end features the medial malleolus

      • Fibula is slender, does not form knee joint; distal end is the lateral malleolus

    • Foot:

    • Composed of tarsals, metatarsals, and phalanges

    • Main tarsal bones: Calcaneus (heel), Talus (ankle)

    • Five metatarsals form the sole; 14 phalanges form the toes

    • Three arches:

      • Medial longitudinal arch, lateral longitudinal arch, transverse arch

      • Supports body weight, acts as a lever for movement

    • Fallen arches referred to as "flat feet"