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By the end of this section, you will be able to:
  • Identify the muscles of the pectoral girdle and upper limbs
  • Identify the movement and function of the pectoral girdle and upper limbs

Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the pectoral girdle, muscles that move the arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers. The pectoral girdle    , or shoulder girdle, consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions.

Muscles that position the pectoral girdle

Muscles that position the pectoral girdle are located either on the anterior thorax or on the posterior thorax ( [link] and [link] ). The anterior muscles include the subclavius    , pectoralis minor    , and serratus anterior    . The posterior muscles include the trapezius    , rhomboid major    , and rhomboid minor    . When the rhomboids are contracted, your scapula moves medially, which can pull the shoulder and upper limb posteriorly.

Muscles that position the pectoral girdle

The left panel shows the anterior lateral view of the pectoral girdle muscle, and the right panel shows the posterior view of the pectoral girdle muscle.
The muscles that stabilize the pectoral girdle make it a steady base on which other muscles can move the arm. Note that the pectoralis major and deltoid, which move the humerus, are cut here to show the deeper positioning muscles.
Muscles that Position the Pectoral Girdle
Position in the thorax Movement Target Target motion direction Prime mover Origin Insertion
Anterior thorax Stabilizes clavicle during movement by depressing it Clavicle Depression Subclavius First rib Inferior surface of clavicle
Anterior thorax Rotates shoulder anteriorly (throwing motion); assists with inhalation Scapula; ribs Scapula: depresses; ribs: elevates Pectoralis minor Anterior surfaces of certain ribs (2–4 or 3–5) Coracoid process of scapula
Anterior thorax Moves arm from side of body to front of body; assists with inhalation Scapula; ribs Scapula: protracts; ribs: elevates Serratus anterior Muscle slips from certain ribs (1–8 or 1–9) Anterior surface of vertebral border of scapula
Posterior thorax Elevates shoulders (shrugging); pulls shoulder blades together; tilts head backwards Scapula; cervical spine Scapula: rotests inferiorly, retracts, elevates, and depresses; spine: extends Trapezius Skull; vertebral column Acromion and spine of scapula; clavicle
Posterior thorax Stabilizes scapula during pectoral girdle movement Scapula Retracts; rotates inferiorly Rhomboid major Thoracic vertebrae (T2–T5) Medial border of scapula
Posterior thorax Stabilizes scapula during pectoral girdle movement Scapula Retracts; rotates inferiorly Rhomboid minor Cervical and thoracic vertebrae (C7 and T1) Medial border of scapula

Muscles that move the humerus

Similar to the muscles that position the pectoral girdle, muscles that cross the shoulder joint and move the humerus bone of the arm include both axial and scapular muscles ( [link] and [link] ). The two axial muscles are the pectoralis major and the latissimus dorsi. The pectoralis major    is thick and fan-shaped, covering much of the superior portion of the anterior thorax. The broad, triangular latissimus dorsi    is located on the inferior part of the back, where it inserts into a thick connective tissue shealth called an aponeurosis.

Questions & Answers

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Esther Reply
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Austine
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Rodgers
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what's the medulla?
alhussiney Reply
The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum
Ludmila
define bone in simple terms
Mhoses Reply
bones are made up by collagen and calcium phosphate
Aurelia
yes
Confidence
Bones are the hard large calcareous connective tissue of which the adult skeleton of most vertebrates is chiefly composed
Olalekan
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Frances
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Mrinal
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Mrinal
Bones protect the various organs of the body
Celina
Bone is a hard strong and durable type of connective tissue
Bkv
bone is a hard, calcareous connective tissue which gives structural support to the body and helpless in its locomotion!
Divya
It also is the main site for synthesis of the RBCs
Divya
A diagram of epithelial tissue
Emmanuel Reply
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marion Reply
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John Reply
Airway resistance in the human lung is? a. Greatest in the generation of distal bronchioles in healthy people because these airways have the smallest radii b. Not increased during a forced expiration in a healthy subject c. Decreased when breathing through the mouth d. Inversely proportional
Maryam Reply
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d
HMD
High
HMD
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menopause
Vasu
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skin
The following hormones increase the blood glucose level except_____________? a. Parathormone b. Growth Hormone c. Epinephrine d. Thyroxine
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Divya
Which of the following is NOT a characteristic feature of alveoli in the lung? a. Poor blood supply b. A large surface area c. Thin walls d. Chemical layer called surfactant
Maryam
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Divya
poor blood supply
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Excess of cortisol causes______________? a. Acromegaly b. Conn’s syndrome c. Diabetes insipidus d. Cushing syndrome
Maryam
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cushing syndrome
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Maryam
Airway resistance in the human lung is? a. Greatest in the generation of distal bronchioles in healthy people because these airways have the smallest radii b. Not increased during a forced expiration in a healthy subject c. Decreased when breathing through the mouth d. Inversely proportional
Maryam
what happens to the brain when one cannot sleep
aghedo
name temporary endocrine gland in female.
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spermatogenesis
Vasu
) Which of the following best describes the human body's defense mechanism against environmental bacteria?
Homeostasis
Zeinab
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skin
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Homeostasis is the system responsible for body response to external changes
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it's a reaction from a body tissue
Perpenjeng
is the body own mechanism of fighting against disease especially infections or injuries.
Azapa
Inflammation is a tissue response to damage tissues
Zeinab
The following hormones increase the blood glucose level except_____________? a. Parathormone b. Growth Hormone c. Epinephrine d. Thyroxine
Maryam
which cells are responsible for bone formation?
Richard Reply
osteocytes
Sharon
Oestocytes
Zeinab
osteocytes
Vasu
The following hormones increase the blood glucose level except_____________? a. Parathormone b. Growth Hormone c. Epinephrine d. Thyroxine
Maryam

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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