Appendicular Skeleton: Bones and Muscles – Lab Practical 3 Study Guide

Overview of Lab Practical 3

Introduction

This study guide covers the major bones and selected muscles of the appendicular skeleton, as outlined for Lab Practical 3 in Anatomy and Physiology I. Students are expected to identify bones, recognize muscle groups, and understand the origins, insertions, and actions of key muscles.

• Appendicular skeleton: Composed of the bones of the limbs and the girdles (pectoral and pelvic) that attach them to the axial skeleton.

• Major focus areas: Bone identification, muscle identification (including cat dissection), and muscle function (origins, insertions, actions).

Pectoral Girdle

Structure and Function

The pectoral girdle connects the upper limb to the axial skeleton and consists of the clavicle and scapula.

• Clavicle: S-shaped bone with a sternal end (medial, articulates with sternum) and an acromial end (lateral, articulates with scapula).

• Scapula: Flat, triangular bone with key features such as the acromion process, coracoid process, glenoid cavity (articulates with humerus), and various borders and fossae (e.g., supraspinous, infraspinous).

Key Terms

• Acromion process: Extension of the scapula forming the highest point of the shoulder.

• Coracoid process: Hook-like structure on the scapula for muscle attachment.

• Glenoid cavity: Shallow socket for articulation with the humerus.

Upper Extremities

Major Bones

The upper limb consists of the humerus, radius, ulna, carpals, metacarpals, and phalanges.

• Humerus: Single bone of the upper arm; articulates with the scapula at the shoulder and with the radius and ulna at the elbow.

• Radius and Ulna: Forearm bones; radius is lateral (thumb side), ulna is medial (pinky side).

• Carpals: Eight wrist bones arranged in two rows.

• Metacarpals: Five bones forming the palm, numbered I (thumb) to V (little finger).

• Phalanges: Fourteen finger bones; each finger has three (proximal, middle, distal) except the thumb, which has two.

Key Features of Humerus

• Head: Articulates with glenoid cavity.

• Greater and lesser tubercles: Muscle attachment sites.

• Deltoid tuberosity: Attachment for deltoid muscle.

• Olecranon fossa: Receives olecranon process of ulna during elbow extension.

Key Features of Radius and Ulna

• Radial tuberosity: Attachment for biceps brachii.

• Styloid process: Distal projection for ligament attachment.

• Olecranon process: Forms the point of the elbow.

• Trochlear notch: Articulates with humerus.

Carpal Bones

Eight carpal bones (proximal and distal rows):

• Scaphoid, Lunate, Triquetrum, Pisiform (proximal row)

• Trapezium, Trapezoid, Capitate, Hamate (distal row)

Pelvic Girdle

Structure and Function

The pelvic girdle is formed by two coxal (os coxae) bones, each resulting from the fusion of the ilium, ischium, and pubis. It attaches the lower limbs to the axial skeleton via articulation with the sacrum.

• Ilium: Superior, broad portion; includes iliac crest and spines.

• Ischium: Inferior, posterior portion; includes ischial tuberosity and spine.

• Pubis: Anterior portion; includes pubic symphysis.

• Acetabulum: Deep socket for femur articulation.

• Obturator foramen: Large opening for nerves and blood vessels.

Male vs. Female Pelvis

• Female pelvis: Broader, wider subpubic angle (>90°), rounder pelvic brim, adapted for childbirth.

• Male pelvis: Narrower, more acute subpubic angle (<90°), heart-shaped pelvic brim.

Lower Extremities

Major Bones

The lower limb consists of the femur, tibia, fibula, tarsals, metatarsals, and phalanges.

• Femur: Thigh bone; longest and strongest bone in the body.

• Tibia: Medial bone of the leg; weight-bearing.

• Fibula: Lateral bone of the leg; non-weight-bearing.

• Patella: Kneecap; articulates with femur.

• Tarsals: Seven ankle bones (talus, calcaneus, navicular, cuboid, medial/intermediate/lateral cuneiforms).

• Metatarsals: Five bones forming the foot arch, numbered I (big toe) to V (little toe).

• Phalanges: Fourteen toe bones; big toe has two, others have three.

Key Features of Femur

• Head: Articulates with acetabulum.

• Greater and lesser trochanters: Muscle attachment sites.

• Medial and lateral condyles: Articulate with tibia.

• Patellar groove: Articulates with patella.

Key Features of Tibia and Fibula

• Tibial tuberosity: Attachment for patellar ligament.

• Medial malleolus: Inner ankle projection.

• Fibular styloid process: Proximal end of fibula.

• Lateral malleolus: Outer ankle projection.

Selected Muscles of the Appendicular Skeleton

Muscles of the Pectoral Girdle (Rotator Cuff)

The rotator cuff stabilizes the shoulder joint and consists of four muscles:

• Supraspinatus: Abducts arm.

• Infraspinatus: Laterally rotates arm.

• Teres minor: Laterally rotates arm.

• Subscapularis: Medially rotates arm.

Muscles of the Shoulder and Arm

• Deltoid: Abducts, flexes, and extends arm.

• Biceps brachii: Flexes elbow and supinates forearm.

• Triceps brachii: Extends elbow.

• Brachialis: Flexes elbow.

Muscles of the Forearm

• Flexor carpi radialis: Flexes and abducts wrist.

• Flexor carpi ulnaris: Flexes and adducts wrist.

• Extensor carpi radialis: Extends and abducts wrist.

• Extensor carpi ulnaris: Extends and adducts wrist.

Muscles of the Torso

• Pectoralis major: Flexes, adducts, and medially rotates arm.

• Rectus abdominis: Flexes vertebral column.

• External and internal oblique: Compress abdomen, flex and rotate trunk.

• Transverse abdominis: Compresses abdomen.

• Gluteus maximus: Extends and laterally rotates thigh.

Muscles of the Thigh and Leg

• Quadriceps femoris: Four muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) that extend the knee.

• Hamstrings: Three muscles (biceps femoris, semimembranosus, semitendinosus) that flex the knee and extend the hip.

• Sartorius: Flexes, abducts, and laterally rotates thigh.

• Gastrocnemius: Plantar flexes foot and flexes knee.

• Soleus: Plantar flexes foot.

• Tibialis anterior: Dorsiflexes and inverts foot.

Muscle Origins, Insertions, and Actions

Definitions

• Origin: The fixed attachment point of a muscle.

• Insertion: The movable attachment point of a muscle.

• Action: The movement produced by muscle contraction.

Example Table: Muscle Origins, Insertions, and Actions

Muscle	Origin	Insertion	Action
Biceps brachii	Scapula	Radial tuberosity	Flexes elbow, supinates forearm
Triceps brachii	Scapula and humerus	Olecranon process of ulna	Extends elbow
Hamstrings	Ischial tuberosity	Tibia and fibula	Flexes knee, extends hip
Gastrocnemius	Medial and lateral condyles of femur	Calcaneus (via Achilles tendon)	Plantar flexes foot, flexes knee

Summary Table: Major Bones of the Appendicular Skeleton

Region	Main Bones	Key Features
Pectoral Girdle	Clavicle, Scapula	Acromion, coracoid, glenoid cavity
Upper Limb	Humerus, Radius, Ulna	Head, tubercles, fossa, styloid process
Hand	Carpals, Metacarpals, Phalanges	Scaphoid, lunate, trapezium, etc.
Pelvic Girdle	Ilium, Ischium, Pubis	Acetabulum, obturator foramen
Lower Limb	Femur, Tibia, Fibula, Patella	Head, trochanters, condyles, malleolus
Foot	Tarsals, Metatarsals, Phalanges	Talus, calcaneus, cuneiforms, etc.

Additional info:

• Students may be required to identify these structures on a dissected cat specimen for muscle identification.

• Understanding anatomical terminology (proximal, distal, medial, lateral) is essential for accurate identification.