Muscle Anatomy Review
Chapter 11 Review Questions
Understanding Muscle Naming Conventions
Understanding muscle naming conventions can assist in identifying various characteristics of muscles such as:
Location: Where the muscle is situated in the body.
Origin: The point where the muscle attaches to the stationary bone.
Insertion: The point where the muscle attaches to the moving bone.
Possible shape: The form of the muscle, such as fusiform, circular, or triangular.
Number of attachment points: This includes how many tendons connect the muscle to the bones (e.g., biceps have two).
Direction of fibers: The alignment of muscle fibers, affecting muscle function (e.g., parallel, oblique).
Size: The overall size of the muscle, which can be described as big, small, etc.
Length: The distance from the origin to the insertion, which influences how much the muscle can contract and generate movement.
The term "biceps brachii" indicates:
Biceps: Two attachment points at the origin.
Brachii: Located in the brachial (arm) region.
Muscles of the Head
Frontal belly of epicranius:
Functions primarily in facial expression.
Location: Forehead
Origin: Frontal bone
Insertion: Epicranial aponeurosis
Shape: Flat
Attachment Points: 2
Direction of Fibers: Horizontal
Size: Moderate
Length: Short
Occipital belly of epicranius:
Also contributes to facial expression and movement of the scalp.
Location: Back of the head
Origin: Occipital bone
Insertion: Epicranial aponeurosis
Shape: Flat
Attachment Points: 2
Direction of Fibers: Horizontal
Size: Moderate
Length: Short
Temporalis:
A muscle involved in mastication (chewing).
Location: Side of the head
Origin: Temporal bone
Insertion: Coronoid process of mandible
Shape: Fan-shaped
Attachment Points: 1
Direction of Fibers: Vertical and horizontal
Size: Large
Length: Moderate
Orbicularis oculi:
Responsible for closing the eyelids; controls blinking and squinting.
Location: Around the eye
Origin: Frontal bone and maxilla
Insertion: Tissue of eyelid
Shape: Circular
Attachment Points: None
Direction of Fibers: Circular
Size: Small
Length: Short
Orbicularis oris:
Surrounds the mouth; involved in puckering and speaking.
Location: Around the mouth
Origin: Maxilla and mandible
Insertion: Skin around the lips
Shape: Circular
Attachment Points: None
Direction of Fibers: Circular
Size: Small
Length: Short
Zygomaticus major:
Elevates the corner of the mouth; responsible for smiling.
Location: Cheek
Origin: Zygomatic bone
Insertion: Skin and muscle at corner of mouth
Shape: Strap-like
Attachment Points: 2
Direction of Fibers: Diagonal
Size: Moderate
Length: Moderate
Buccinator:
Presses the cheek against the teeth; assists in chewing.
Location: Cheek
Origin: Maxilla and mandible
Insertion: Orbicularis oris
Shape: Quadrilateral
Attachment Points: 2
Direction of Fibers: Horizontal
Size: Moderate
Length: Moderate
Major Muscle of the Neck
Sternocleidomastoid:
Rotates and flexes the head.
Location: Neck
Origin: Sternum and clavicle
Insertion: Mastoid process of temporal bone
Shape: Long and slender
Attachment Points: 2
Direction of Fibers: Diagonal
Size: Large
Length: Long
Platysma:
Tenses the skin of the neck; contributes to facial expressions.
Location: Neck and jaw region
Origin: Fascia of the chest
Insertion: Mandible and skin of the lower face
Shape: Thin and broad
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Long
Muscles of the Abdominal Wall
Rectus abdominis:
Flexes the torso and compresses abdominal contents.
Location: Abdomen
Origin: Pubic symphysis
Insertion: Xiphoid process and costal cartilages
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Vertical
Size: Large
Length: Long
Transversus abdominis:
Compresses the abdominal contents; stabilizes the pelvis.
Location: Abdomen
Origin: Iliac crest and costal cartilages
Insertion: Linea alba
Shape: Flat
Attachment Points: 1
Direction of Fibers: Horizontal
Size: Medium
Length: Moderate
External oblique:
Flexes and rotates the trunk; aids in lateral flexion.
Location: Lateral abdomen
Origin: Lower 8 ribs
Insertion: Iliac crest and linea alba
Shape: Flat
Attachment Points: 2
Direction of Fibers: Diagonal
Size: Large
Length: Long
Internal oblique:
Works similarly to the external oblique but fibers run in the opposite direction.
Location: Lateral abdomen
Origin: Iliac crest
Insertion: Lower 3 ribs and linea alba
Shape: Flat
Attachment Points: 2
Direction of Fibers: Diagonal
Size: Large
Length: Long
Muscles of the Anterior Thorax
Serratus anterior:
Protracts the scapula; aids in upward rotation.
Location: Lateral thorax
Origin: Ribs 1-8
Insertion: Anterior surface of the scapula
Shape: Saw-toothed
Attachment Points: 8
Direction of Fibers: Horizontal
Size: Medium
Length: Moderate
Pectoralis major:
Major muscle for arm flexion, adduction, and rotation.
Location: Chest
Origin: Clavicle, sternum, and ribs 1-6
Insertion: Greater tubercle of humerus
Shape: Fan-shaped
Attachment Points: 3
Direction of Fibers: Diagonal
Size: Large
Length: Long
Muscles of the Posterior Thorax
Levator scapulae:
Elevates the scapula; assists with neck movements.
Location: Back of neck
Origin: Transverse processes of C1-C4
Insertion: Superior part of medial border of scapula
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Moderate
Trapezius:
Elevates, retracts, and rotates the scapula; extends neck.
Location: Upper back
Origin: Occipital bone and C7-T12
Insertion: Clavicle and spine of scapula
Shape: Trapezoidal
Attachment Points: 3
Direction of Fibers: Multiple directions
Size: Large
Length: Long
Muscle of the Back
Latissimus dorsi:
Responsible for extension, adduction, and medial rotation of the arm.
Location: Lower back
Origin: T7-L5, sacrum, and iliac crest
Insertion: Intertubercular groove of humerus
Shape: Flat and broad
Attachment Points: 1
Direction of Fibers: Converging
Size: Large
Length: Long
Shoulder Muscles
Deltoid:
Abducts, flexes, and extends the shoulder joint.
Location: Shoulder
Origin: Clavicle and scapula
Insertion: Deltoid tuberosity of humerus
Shape: Triangular
Attachment Points: 2
Direction of Fibers: Multiple directions
Size: Large
Length: Moderate
Muscles of the Arm and Forearm
Biceps brachii:
Flexes the elbow and supinates the forearm.
Location: Anterior arm
Origin: Scapula (2 locations)
Insertion: Radial tuberosity
Shape: Fusiform
Attachment Points: 2
Direction of Fibers: Parallel
Size: Medium
Length: Moderate
Triceps brachii:
Extends the elbow.
Location: Posterior arm
Origin: Scapula and humerus (2 locations)
Insertion: Olecranon of the ulna
Shape: Fusiform
Attachment Points: 3
Direction of Fibers: Parallel
Size: Large
Length: Long
Brachialis:
Major flexor of the elbow.
Location: Anterior arm beneath biceps
Origin: Humerus
Insertion: Coronoid process of the ulna
Shape: Flat
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Short
Muscles Crossing Hip Joint
Sartorius:
Flexes, abducts, and laterally rotates the hip; assists in flexing the knee.
Location: Thigh
Origin: Anterior superior iliac spine
Insertion: Medial aspect of proximal tibia
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Diagonal
Size: Long and thin
Length: Long
Gracilis:
Adducts the thigh and aids in knee flexion.
Location: Inner thigh
Origin: Pubic symphysis
Insertion: Medial aspect of proximal tibia
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Long
Quadriceps femoris:
Composed of four muscles:
Rectus femoris:
Extends the knee and helps flex the hip.
Location: Anterior thigh
Origin: Anterior inferior iliac spine and acetabulum
Insertion: Tibial tuberosity via patellar ligament
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Vertical
Size: Large
Length: Long
Vastus lateralis:
Extends the knee.
Location: Lateral thigh
Origin: Greater trochanter and linea aspera
Insertion: Tibial tuberosity via patellar ligament
Shape: Flat
Attachment Points: 1
Direction of Fibers: Vertical
Size: Large
Length: Long
Vastus medialis:
Extends the knee.
Location: Medial thigh
Origin: Linea aspera
Insertion: Tibial tuberosity via patellar ligament
Shape: Flat
Attachment Points: 1
Direction of Fibers: Vertical
Size: Large
Length: Long
Vastus intermedius:
Extends the knee.
Location: Deep to rectus femoris
Origin: Anterior and lateral femur
Insertion: Tibial tuberosity via patellar ligament
Shape: Flat
Attachment Points: 1
Direction of Fibers: Vertical
Size: Large
Length: Long
Gluteus maximus:
Extends and laterally rotates the hip.
Location: Buttocks
Origin: Ilium, sacrum, and coccyx
Insertion: Gluteal tuberosity of femur
Shape: Convergent
Attachment Points: 1
Direction of Fibers: Diagonal
Size: Large
Length: Long
Hamstrings:
Composed of three muscles:
Biceps femoris:
Flexes the knee and aids in hip extension.
Location: Posterior thigh
Origin: Ischial tuberosity and linea aspera
Insertion: Head of fibula and lateral condyle of tibia
Shape: Strap-like
Attachment Points: 2
Direction of Fibers: Vertical
Size: Large
Length: Long
Semitendinosus:
Flexes the knee; extends the hip.
Location: Posterior thigh
Origin: Ischial tuberosity
Insertion: Proximal tibia
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Long
Semimembranosus:
Flexes the knee; extends the hip.
Location: Posterior thigh
Origin: Ischial tuberosity
Insertion: Medial condyle of tibia
Shape: Flat
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Long
Adductors:
Composed of two major muscles:
Adductor magnus:
Adducts and extends the thigh.
Location: Medial thigh
Origin: Ischium and pubis
Insertion: Linea aspera of femur
Shape: Fan-shaped
Attachment Points: 2
Direction of Fibers: Vertical
Size: Large
Length: Long
Adductor longus:
Adducts the thigh and assists in flexion.
Location: Medial thigh
Origin: Pubis
Insertion: Midshaft of femur
Shape: Flat
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Long
Muscles of the Leg
Gastrocnemius:
Plantar flexes the foot and flexes the knee.
Location: Posterior leg
Origin: Medial and lateral condyles of femur
Insertion: Calcaneus via Achilles tendon
Shape: Two-headed
Attachment Points: 2
Direction of Fibers: Vertical
Size: Large
Length: Long
Soleus:
Primarily responsible for plantar flexion of the foot.
Location: Posterior leg beneath gastrocnemius
Origin: Head of fibula and medial tibia
Insertion: Calcaneus via Achilles tendon
Shape: Flat
Attachment Points: 1
Direction of Fibers: Horizontal
Size: Large
Length: Moderate
Tibialis anterior:
Dorsiflexes the foot and inverts the ankle.
Location: Anterior leg
Origin: Lateral condyle and tibia
Insertion: Medial cuneiform and first metatarsal
Shape: Strap-like
Attachment Points: 1
Direction of Fibers: Vertical
Size: Medium
Length: Short