Appendicular Skeleton

Overview

• The appendicular skeleton comprises various bones and structures that facilitate movement and support.

• Main components include:

  • Skull

  • Clavicle

  • Scapula

  • Sternum

  • Rib

  • Humerus

  • 126 bones of limbs

  • Pectoral girdle

  • Pelvic girdle

  • Spine (vertebrae)

  • Coccyx

  • Bones of the lower limbs include:

  • Radius

  • Ulna

  • Carpals

  • Metacarpals

  • Phalanges

  • Femur

  • Patella

  • Tibia

  • Fibula

  • Tarsals

  • Metatarsals

  • Phalanges

Shoulder Girdle

• The shoulder girdle, also known as the pectoral girdle, consists of:

  • Clavicle and Scapula

Clavicle

• Function:

  • Attaches medially to the manubrium of the sternum and laterally to the scapula.

  • Acts as a brace to keep the arm away from the thorax, helping to prevent shoulder dislocation.

Structure of Clavicle

• The clavicle has two ends:

  • Sternal (medial) end

  • Acromial (lateral) end

  • Views of the right clavicle:

  • Superior view

  • Inferior view

Scapula

• Description:

  • Triangular shape and flares when arms are moved posteriorly.

  • Not directly attached to the axial skeleton; held in place by muscles.

• Structure includes:

  • Flattened body

  • Acromion: enlarged end of the spine of the scapula.

  • Coracoid Process: projects over the top of the shoulder, anchoring arm muscles.

Anatomical Features of Scapula

• Significant markings include:

  • Acromioclavicular joint: where acromion connects with the clavicle.

  • Suprascapular notch: a nerve passageway.

  • Glenoid Cavity: shallow socket for the head of the humerus.

Mobility of the Shoulder Girdle

• The design of the shoulder girdle allows significant mobility due to:

  1. Sternoclavicular joint: the only attachment to the axial skeleton.

  2. Loose attachments allow sliding against the thorax as muscles move.

  3. The shallowness of the glenoid cavity and weak reinforcement by ligaments at the shoulder joint.

Upper Limbs

• Composed of 30 bones including the arm, forearm, and hand.

Arm

• Characterized by a single bone:

  • Humerus: a typical long bone.

  • Proximal end fits into the glenoid cavity.

  • Key anatomical features:

  • Greater tubercle

  • Lesser tubercle

  • Head of humerus

  • Anatomical neck

  • Intertubercular groove

  • Surgical neck

  • Radial groove

  • Deltoid tuberosity

  • Medial and lateral supracondylar ridges

  • Coronoid fossa

  • Radial fossa

  • Olecranon fossa

  • Medial and lateral epicondyles

  • Capitulum and Trochlea

Forearm

• Composed of two bones:

  • Radius and Ulna.

  • In anatomical position, radius is lateral.

  • Key features include:

  • Radioulnar joints at both ends.

  • Interosseous membrane connecting the two bones.

Hand

• Comprised of carpals, metacarpals, and phalanges:

  • 8 Carpals: arranged in two irregular rows of 4, forming the carpus (wrist).

  • Metacarpals: numbered 1-5 from the thumb to the little finger; heads form the knuckles.

  • Phalanges: total of 14; 3 in each finger except the thumb (which has 2).

Pelvic Girdle

• Composed of two coxal bones (hip bones) and the sacrum.

• Forms the pelvis in conjunction with the coccyx.

• Key functions:

  • Weight-bearing is the primary function of the pelvic girdle.

Structure of Pelvic Girdle

• Comprises:

  • Fusion of ilium, ischium, and pubis.

  • Notable features include:

  • Iliac crest

  • Sacroiliac joint

  • Greater sciatic notch

  • Ischial tuberosity

  • Acetabulum (socket for the head of the femur)

• Anterior structures:

  • Pubis

  • Ischium

  • Pubic symphysis

Gender Differences in Pelvis

• Females:

  • Wider iliac crest and a larger pelvic cavity.

  • Greater sciatic notch.

  • Broad pelvic outlet important for childbirth.

• Males:

  • Narrower iliac crest and pelvic cavity.

  • Less prominent greater sciatic notch.

Lower Limbs

• Functions primarily to bear total body weight in an erect position.

• Divided into three segments:

  • Thigh

  • Leg

  • Foot

Thigh

• Contains one bone:

  • Femur: the heaviest and strongest bone in the body.

  • Anatomical details:

  • Slants medially to align the knees with the center of gravity.

  • More noticeable in females due to pelvic shape.

Leg

• Composed of:

  • Tibia and Fibula.

  • Connected by interosseous tissue.

  • Key features:

  • Tibial tuberosity

  • Intercondylar eminence

  • Medial and lateral condyles

  • Distal and proximal tibiofibular joints

Foot

• Comprised of tarsals, metatarsals, and phalanges:

  • 7 Tarsals: including the calcaneus and talus.

  • 5 Metatarsals.

  • 14 Phalanges.

• Purpose:

  • Supports body weight and acts as a lever for movement during walking and running.

  • Arranged in 3 arches (2 longitudinal and 1 transverse) supported by ligaments and tendons to maintain shape.