BIOD 151 / BIOD151 ANATOMY AND PHYSIOLOGY MODULE 5
Anatomy of the Muscular System: Introduction & Muscles of the Head, Neck, and Trunk
Notice: To
... [Show More] optimize your learning in this course, we advise that you complete the labs and modules as indicated in the BIOD 151 Lab Schedule.
The muscular system and the skeletal system work together to provide movement for the human body. Muscle tissue is found in three distinct types in the body; skeletal, smooth, and cardiac.
Skeletal muscles must have a blood and nervous supply to provide movement. Skeletal muscles are under conscious control, meaning that a person can consciously decide to use these muscles to complete an action. Communication within the body to coordinate movement starts in the brain with a message that is sent through the spinal cord and eventually attaches to a muscle. Peripheral nerves carry the signal from the central nervous system (brain and spinal cord) to a specific muscle destination to provide movement. Messages from the central nervous system to a muscle are called a motor actions. Nerves also carry information from the external environment to the central nervous system, called sensation or sensory input. (see Figure 5.1 and Figure 5.2) Spinal nerves combine to form complex networks of peripheral nerves throughout the body.
Figure 5.1 Posterior view of the nervous system. The brain and spinal cord (central nervous
system) connect to the peripheral nervous system. Examples of peripheral nerves are spinal nerves (cervical, thoracic, and lumbar), the upper trunk of the brachial plexus, and the radial nerve.
Figure 5.2 Peripheral nerves carry the communication from the central nervous system (brain and spinal cord) to the muscle. Peripheral nerves also carry information from the environment to the central nervous system.
Tendons are connective tissues that connect skeletal muscle to bone at each end (see Figure 5.3).
Tendons are flexible, can bend at the joints, and help cushion against sudden
movement. Ligaments are connective tissue that connects bone to bone, helping to stabilize joints where bones meet.
Figure 5.3 Skeletal muscles attach to bones via tendons at points called the origin and insertion. The origin is the fixed point while the insertion is the place that is moved during a muscle contraction.
All skeletal muscles have an origin, insertion, and action. The origin is the bony site of attachment which is stationary during the movement. The insertion of a muscle is the bony site of attachment that is moved by the muscle contraction. (see Figure 5.3)
The origin and insertion can be reversed in different types of movement. For this module, the standard origin and insertion points are referenced from anatomical position.
The action of the muscle is what effect is produced by the muscle’s contraction. For example, the triceps is the primary extensor of the forearm. The innervation is the peripheral nerve that supplies a muscle with the message from the brain. For example, the innervation of the biceps brachii is the musculocutaneous nerve. (see Figure 5.4)
Figure 5.4 Anterior view of the musculocutaneous nerve (blue) innervates the biceps brachii muscle.
Muscles are generally studied in groups. The following muscle list is an overview of some of the major muscles in the body. Study the location of the muscle in the body. In addition, if listed, study the origin, insertion, innervation and action of these muscles.
Muscles of Facial Expression: (See Figure 5.5)
The muscles in this grouping help to facilitate all the actions within the face. All the varied facial expressions are enabled by these muscles. CN is an abbreviation for cranial nerve. There are twelve pairs of cranial nerves that originate on the ventral surface of the brain, controlling muscles and functions of several organs and glands.
Orbicularis oculi
Action: eye closure
Innervation: Facial nerve (CN VII)
Orbicularis oris
Action: mouth closure: closes lips, protrudes lips forward, presses lips against teeth
Innervation: Facial nerve (CN VII)
Zygomaticus major/minor
Action: pull corners of lips upward Innervation: Facial nerve (CN VII)
Risorius
Action: pulls the corners of the mouth posteriorly (grin or grimace) Innervation: Facial nerve (CN VII)
Frontalis (occipitofrontailis) Action: raise eyebrows Innervation: Facial nerve (CN VII)
Buccinator
Action: compress cheeks Innervation: Facial nerve (CN VII)
Masseter
Action: jaw closure
Innervation: Trigeminal nerve (CN V, mandibular branch)
Temporalis
Action: Elevates mandible, closes jaw
Innervation: Trigeminal nerve (CN V, mandibular branch)
Figure 5.5 Muscles of facial expression. Note that the buccinator is deep to zygomaticus major/minor and risorius.
Muscles of the Head and Neck: (See Figure 5.6)
The muscles in this grouping help to facilitate actions which move the head (occiput) and control the neck. Side bending of the neck is also called side flexion or lateral flexion, which refers to moving one of the ears to the same side shoulder. Neck flexion refers to the action of moving the chin towards the sternum. Note there are several muscles that have differing actions if acting together on both sides (bilaterally) or acting on one side only (unilaterally).
Semispinalis Capitis
Origin: Articular processes of inferior cervical & transverse process of superior thoracic vertebrae Insertion: Occipital bone
Action:
Bilateral extend head
Unilateral laterally flexes neck to same side Innervation: Spinal nerves
Sternocleidomastoid
Origin: Sternal end of clavicle and manubrium Insertion: Mastoid region of skull
Action:
Bilateral: Neck flexion
Unilateral: Turns face to opposite side Innervation: Accessory nerve (CN XI)
Splenius Capitis
Origin: Spinous process/ligaments of inferior cervical vertebrae Insertion: Mastoid process, occipital bones of skull
Action:
Bilateral extend head
Unilateral laterally flexes neck to same side Innervation: Cervical spinal nerves
Longissimus cervicis
Origin: transverse processes of superior thoracic vertebrae
Insertion: transverse process of middle and superior cervical vertebrae Action:
Bilateral extend head
Unilateral laterally flexes neck to same side Innervation: Cervical and thoracic spinal nerves
Longissimus thoracis
Origin: Transverse process of inferior thoracic, superior lumbar vertebrae Insertion: Transverse process of middle and superior cervical vertebrae Action:
Bilateral extend head
Unilateral laterally flexes neck to same side Innervation: Thoracic and lumbar spinal nerves
Thyrohyoid
Origin: Thyroid cartilage of larynx Insertion: Hyoid bone
Action: Elevates thyroid, depresses hyoid bone Innervation: Hypoglossal nerve
Scalenes (anterior, middle, posterior) Origin: Transverse processes of C2- C7 Insertion: 1st and 2nd Ribs
Action: Elevates ribs 1 & 2 Innervation: Cervical spinal nerves
Figure 5.6 Lateral view: Muscles of the head and neck
Vertebral Column: Erector Spinae (See Figure 5.7)
The erector spinae group are superficial muscles in the back. These muscles act as the prime extensors of the vertebral column. Flexion of the spine refers to forward bending the trunk (such as a “cat” stretch). Extension of the spine refers backward bending. The vertebral column is also able to perform side bending (or lateral flexion) as well as movement around an axis (rotation).
Spinalis:
Medial column of erector spinae
Made up of three divisions (spinalis thoracis, spinalis cervicis, and spinalis capitis)
Longissimus:
Intermediate column of erector spinae
Made up of three divisions (longissimus dorsi, longissimus cervicis, longissimus capitits)
Iliocostalis:
Lateral column of erector spinae
Made up of three divisions (iliocostalis lumborum, iliocostalis thoracis, iliocostalis cervicis)
Figure 5.7 Posterior view: Erector Spinae Group
Oblique and rectus muscles: Anterior (See Figure 5.8)
The abdominal muscles perform many functions. These muscles help to support and protect the abdominal viscera (which are not protected by bony structures). These muscles, along with the muscles in the back (see above) help to provide support for upright posture and balance.
Rectus abdominis
Origin: Pubic Crest, pubic symphysis
Insertion: Pubis, cartilages of ribs 5-7, xiphoid process
Action: Flexion of spine, compression of abdominal viscera Innervation: Spinal nerves (T 7-T 12)
External oblique
Origin: Sternum, ribs (5-12) Insertion: Linea alba, iliac crest Action:
Bilaterally: Flexion of the spine, compress the abdomen; Unilaterally: Flexes trunk to same side, rotates to opposite side
Innervation: Lower intercostal, ilioinguinal nerves
Internal oblique
Origin: Iliac crest, lumbodorsal fascia Insertion: Inferior ribs, linea alba
Action: Compresses abdomen, depresses ribs, flexes spine Innervation: Lower intercostal, ilioinguinal nerves
Transverse abdominis – deep to internal oblique Origin: Lateral inguinal ligament, inner iliac crest Insertion: Linea alba, pubis
Action: Compression of abdomen
Innervation: First lumbar nerve (T 7- L1), iliohypogastric (T12-L1), ilioinguinal (T12-L1)
Figure 5.8 Muscles and landmarks of the anterior trunk
Muscles of Breathing (See Figure 5.9)
The diaphragm is the primary muscle necessary for intaking air. The internal intercostals and the external intercostals work in opposite functions. Notice the difference in their muscle fiber orientation (see Figure 5.9).
Diaphragm
Origin: Cartilage of ribs 7-12, xiphoid process, lumbar vertebrae Insertion: Anterior longitudinal ligament (vertebral column) Action: Expands thoracic cavity, compresses abdominal cavity Innervation: Phrenic nerve (C3-5)
Internal Intercostals
Origin: Superior border of ribs 2-12 Insertion: Inferior of ribs above (1-11) Action: Depresses ribs (forced expiration) Innervation: Intercostal nerves
External Intercostals
Origin: Lower border of ribs 1-11
Insertion: Upper border of ribs below (1-12) Action: Elevates ribs (normal inspiration) Innervation: Intercostal nerves
Figure 5.9 Anterior view of the muscles of breathing. The diaphragm is the primary muscle of inspiration.
Anatomy of the Muscular System Part II: Muscles of the Upper and Lower Extremities
Muscles of the Shoulder and Upper Extremity (See Figures 5.10, 5.11, 5.12)
The muscles on the posterior thorax assist in movement of the shoulder girdle. The trapezius is a large muscle that acts on the shoulder as well as the neck and upper spine. The trapezius is superficial to the remaining muscles shown (see Figure 5.10).
Trapezius (upper, middle, lower)
Origin: Occipital bone, spinous process of T1-12,
Insertion: Lateral clavicle, acromion, and scapular spine of scapula
Action: Rotation, retraction, elevation, depression of scapula; extends neck; stabilizes shoulder Innervation: Accessory nerve (Cranial Nerve 11)
Levator scapulae
Origin: Transverse process of C1-4 Insertion: Medial border of scapula Action: Elevates scapula Innervation: Dorsal scapular nerve
Rhomboids (major, minor)
Origin: Spinous process (minor: C7-T1) (major: T2-5) Insertion: Medial border of scapula
Action: Retraction of scapula Innervation: Dorsal scapular nerve
Figure 5.10 Posterior view of the shoulder girdle muscles. The trapezius is a superficial muscle (shown on left). On the right, the trapezius is cut away to show the muscles underneath.
*Note: Additional muscles are labeled in this figure for clarification.
Pectoralis minor
Origin: Ribs 3-5
Insertion: Coracoid process of scapula
Action: Elevates ribs, draws scapula down and medially Innervation: Medial pectoral nerve
Serratus Anterior
Origin: Upper 8-9 ribs
Insertion: Medial border of scapula Action: Protraction of scapula Innervation: Long thoracic nerve
Figure 5.11 Anterior view of the muscles of the thorax and shoulder girdle. Serratus anterior (left and right) is highlighted in blue.
Muscles of the shoulder girdle continued: (See Figures 5.12, 5.13, 5.14)
The shoulder is a ball and socket joint, which permits many types of movement. The glenoid cavity of the scapula is very small compared to the head of the humerus. The large bony structure of the shoulder requires many ligaments and layers of muscle for stability. A muscle grouping known as
the rotator cuff is necessary to stabilize the humeral head inside the shoulder joint. The rotator cuff is made up of the “SITS” muscles: Supraspinatus, Infraspinatus, Teres minor, and Subscapularis. (See Figure 5.14)
Deltoid (anterior, posterior, middle) Origin: Clavicle and scapula
Insertion: Deltoid tuberosity of humerus Action: Abduction at shoulder (whole muscle) Innervation: Axillary nerve
Pectoralis major
Origin: Ribs 2-6, body of sternum Insertion: Greater tubercle of humerus
Action: Flexion, adduction and medial rotation at shoulder Innervation: Pectoral Nerves
Supraspinatus- (above spine of scapula) Origin: Supraspinatus fossa of scapula Insertion: Greater tubercle of humerus Action: Abduction at the shoulder Innervation: Suprascapular nerve
Infraspinatus (below spine of scapula) Origin: Infraspinatus fossa of scapula Insertion: Greater tubercle of humerus Action: Lateral rotation at shoulder Innervation: Suprascapular nerve
Teres Minor
Origin: Lateral border of scapula Insertion: Greater tubercle of humerus Action: Lateral rotation at shoulder Innervation: Axillary nerve
Teres Major – not part of the rotator cuff Origin: Inferior angle of scapula
Insertion: Intertubercular groove of humerus
Action: Extension, adduction, and medial rotation at shoulder Innervation: Lower subscapular nerve
Subscapularis- along inner surface of the scapula Origin: Subscapular fossa of scapula
Insertion: Lesser tubercle of humerus Action: Medial rotation at the shoulder Innervation: Subscapular nerves
Latissimus Dorsi
Origin: Spinous process of inferior thoracic and lumbar vertebrae, ribs 8-12 Insertion: Intertubercular groove of humerus
Action: Extension, adduction, and medial rotation at shoulder Innervation: Thoracodorsal nerve
Coracobrachialis
Origin: Coracoid process of scapula Insertion: Medial shaft of humerus Action: Adduction and flexion at shoulder Innervation: Musculocutaneous nerve [Show Less]