Pectoral Girdle
Pectoral Girdle
The pectoral girdle (or shoulder girdle) is a set of bones found in the appendicular skeleton that connects the arms to the axial skeleton. In humans, the pectoral girdle consists of the clavicle (collarbone) and the scapula (shoulder blade). These girdles support the appendages of the axial skeleton.
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The pectoral girdle is part of the appendicular skeleton, which connects the upper limbs to the axial skeleton. The human skeleton is divided into two sections, the axial skeleton and the appendicular skeleton. The axial skeleton is made up of 80 bones and includes the skull, the vertebral column, ribs and the sternum. The appendicular skeleton is made up of 126 bones and includes the pectoral girdle, the pelvic girdle and limbs. The pectoral girdle is also known as shoulder girdle. It constitutes the shoulder part and is also the attachment site for the humerus.
Pectoral Girdle Bones
The Pectoral Girdle can be divided into two equal halves. Each half consists of two bones: the Scapula (Shoulder Blade) and the Clavicle (Collar Bone). This girdle helps in the articulation of the upper limbs to the axial skeleton, and aids in the movement of the arms and shoulders. The right and left parts of the girdle are not joined together, allowing for independent movement.
The main parts of the pectoral girdle are:
Scapula (Shoulder Blade)
The triangular-shaped flat bone located dorsally in the thorax region between the second and seventh ribs forms the posterior side of the shoulder.
The Spine of the Scapula
The spine of the scapula is an elevated ridge located on the posterior side of the scapula. It divides the convex posterior portion of the scapula into two parts: the smaller supraspinous fossa and the larger infraspinous fossa.
The ventral surface of the scapula faces the ribs, and there is a concave depression known as the subscapular fossa.
Acromion: It is a flat and expanded process of the spine that extends laterally. It articulates with the clavicle by the acromioclavicular joint and forms an arch over the glenohumeral joint.
Glenoid Cavity: It is located beneath the acromion and is a depression on the lateral side of the scapula. The head of the humerus connects to the glenoid cavity at the glenohumeral joint.
Coracoid Process: It is a hook-like projection located above the glenoid cavity and below the clavicle. It is connected to the clavicle by a ligament, and muscles of the arms and chest attach to it.
Pectoral Girdle Image
Below is a well labelled diagram of the pectoral girdle for better understanding:
Pectoral Girdle Image
Clavicle (Collar Bone)
The clavicle is a long s-shaped bone that forms the anterior part of the pectoral girdle. It is present horizontally and is also known as the collar bone.
The clavicle’s primary purpose is to connect the upper limb to the sternum (axial skeleton) and transmit forces from the upper limb to the axial skeleton. Additionally, it protects the underlying nerves and vasculature, which links the upper limb to the trunk.
On one side, it articulates with the sternum and on the other, it articulates with the acromion.
The large and triangular sternal end, also known as the medial part, articulates with the manubrium of the sternum through the sternoclavicular joint. It is supported by the costoclavicular ligament or rhomboid ligament located between the clavicle and the first rib.
Many muscles attach to the shaft portion of the bone, including the deltoid, trapezius, and sternohyoid muscles.
The acromial end, also known as the lateral part, articulates with the acromion of the scapula by the acromioclavicular joint. It forms the bony tip of the shoulder laterally and is attached to the conoid and trapezoid ligaments.
See Also: Locomotion and Movement
In conclusion, the Pectoral Girdle is composed of two bones, the scapula and clavicle, and connects the upper limb to the trunk. It is only connected to the vertebral column by ligaments, allowing for more range of motion than the Pelvic Girdle. The Sternoclavicular joints on both sides are the only true joints between the Pectoral Girdle and the Axial Skeleton.
Pectoral Muscle
The pectoral muscles are a group of skeletal muscles that connect the upper edges of the chest to the lateral and anterior thoracic walls. These muscles are responsible for a range of motions, such as adduction, flexion, internal rotation of the humerus, stabilization of the scapula, depressing and elevating of the bones of the thorax, and more.
The main muscles that participate in these actions are:
Pectoralis Minor
The Pectoralis minor is a triangular, thin muscle that is attached to the ribs and is found under the Pectoralis major. It plays an important role in stabilizing the scapula.
Pectoralis Major
The Pectoralis major is a fan-shaped, thick muscle found under the breast. It functions in extending, flexing, and rotating the humerus, which is the long bone of the upper arm.
Subclavius
The subclavius muscle, along with pectoralis minor and pectoralis major, is responsible for movement in the axilla (or armpit). This muscle is responsible for the movement of the shoulder forward and downward.
Serratus Anterior
The Serratus anterior, located anteriorly on the chest, assists in the forward rotation of the scapula around the torso.
Frequently Asked Questions
Pectoral Girdle
Pectoral girdle refers to the bones and cartilage that connect the upper limb to the axial skeleton. It consists of the clavicles and the scapulae, which are connected by muscles and ligaments.
The pectoral girdle (shoulder girdle) is a set of bones found in the appendicular skeleton connecting the arm on either side. The pectoral girdle in humans comprises the clavicle and the scapula. The girdles support the appendages to the axial skeleton.
The pectoral girdle is formed by the clavicle and the scapula, and its function is to connect the upper limb to the axial skeleton.
The pectoral girdle is made up of two bones, namely clavicle and scapula. The scapula, also known as the shoulder blade, is present posteriorly in the shoulder. It helps in articulation with the collarbone and humerus bone. The clavicle, also known as the collarbone, is present anteriorly to the shoulder. It helps in articulation with the sternum and acromion.
What Are the Movements Possible at the Shoulder Girdle?
The joints in the shoulder girdle are synovial joints that allow upward and downward movement of the humerus away and towards the body. It allows flexion and extension, that is the movement of the humerus anteriorly and posteriorly. Additionally, it also facilitates rotation of the humerus and horizontal movement away and towards the chest.
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