Appendicular Skeleton: Meaning, Diagram, Functions

Appendicular Skeleton: A human body is made up of approximately 206 to 213 different bones. These bones are part of the skeleton that helps us in every movement and the organs in our body. The skeleton or the bone structure is of two categories: Axial skeleton and Appendicular skeleton. The appendicular skeleton is made up of the bones of the upper and lower limbs that help in locomotion.

The appendicular skeleton contains the pectoral girdle, which connects the upper limbs to the body, and the pelvic girdle connects the lower limbs to the body. There are 126 bones in a human appendicular skeleton. In this article, let’s learn everything about the Appendicular Skeleton system, diagram of appendicular skeleton, appendicular skeleton bones list & much more.

Define Appendicular Skeleton

The bones of the limbs along with their girdles constitute the appendicular skeleton.

Source: NCERT

What is a Human Skeletal System?

The Human Skeletal system consists of a framework of bones and a few cartilages. This system has a significant role in the movement shown by the body. (Source: NCERT)

The skeletal system of humans can be basically divided into two parts (i) the axial skeleton and (ii) the appendicular skeleton.

This Appendicular Skeletal system is associated with the appendages of our body.

What is Appendicular Skeleton?

The appendicular skeleton consists of two girdles, the pectoral girdle and the pelvic girdle. This includes the bones of the upper and lower limbs. It consists of \(126\) bones. It allows us to move and manipulate objects.

Diagram of Appendicular Skeleton

Figure: Appendicular Skeleton

Parts

Now let’s discuss Appendicular Skeleton Parts in detail:

Appendicular Skeleton: 

Appendicular Skeleton: 
The different components of the appendicular skeleton are as follows:

1. Pectoral girdle
2. Pelvic girdle
3. The Upper limbs or forearm
4. The lower limbs or hindlimb

1. Pectoral girdle: The pectoral girdle is a set of bones that connects the upper limbs to the axial skeleton on each side. It is also known as the shoulder girdle. The human body consists of two major bones, the clavicle and scapula.

(1) The Clavicles:

1. It is also known as collar bones.
2. Long slender bones with two curvatures.
3. It originates at the manubrium.
4. It helps in articulation of the upper limb with the axial skeleton.

(2) The Scapula:

1. It is also known as shoulder blades.
2. It is broad, flat, and triangular.
3. It lies on the dorsal side of the thorax.
4. It is located between the second and seventh ribs.
5. The scapula’s dorsal, flat, triangular body consists of a sharp ridge called the spine.
6. The end of the spine projects as a flattened and expanded portion called the acromion. This articulates with the arm and collar bone.
7. The Glenoid cavity is the depression that is present below the acromion where the head of the humerus articulates to form the shoulder joint.
8. The lateral ends of the superior scapula is a projection of the anterior surface called the Coracoid process. The tendons of muscle attach to this.

Functions of Pectoral Girdle:

1. This provides an attachment point of numerous muscles which are needed to move the forearm.
2. This also provides connections between the upper extremities (arms) and the axial skeleton.

Figure: Pectoral Girdle

2. Pelvic girdle: The pelvic girdle is also called pelvis or Hip girdle. It is in the lower part of the trunk. The pelvic girdle is a composition of bones that functions as the point of attachment of the lower limbs to the axial skeleton. It comprises two coxal bones or hip bones.

1. Coxal bone (hip bones) is also called ossa coxae or innominate bone. 
2. Each coxal bone comprises three fused bones: the upper ilium, the lower ischium, and the inner pubis.
3. The ilium is the superior most.
4. The ischium is inferior and posterior.
5. The pubis is inferior and anterior.
6. The hip joint socket is the acetabulum, which is deep and cup-shaped. In this, the head of the femur articulates.
7. The two halves of the pelvic girdle meet ventrally to form pubic symphysis containing fibrous cartilage.
8. The ilium has one large depression called the greater sciatic notch. The ischium has another small depression, called the lesser sciatic notch.

Functions of Pelvic Girdle:

1. This provides an attachment point of numerous muscles which are needed to move the legs.
2. This carries the complete weight of our vertebral column and body.
3. This supports the lower body organs including urinary bladder, reproductive organs.

Figure: Pelvic Girdle

3. The Upper limbs or forearm: The upper limb or forearm is also known as antebrachium. It contains a total of \(60\) bones, i.e., \(30\) on each side. The upper limb consists of the following bones: humerus, radius, ulna, carpals or wrist bones, metacarpals or palm bones and phalanges or digits.
(1) Humerus: It is a long bone of the upper limb with a rounded head, a v-shaped ridge and a flat lower end; it extends from the shoulder to the elbow. There are two humerus bones, one in each hand.
(2) Radius: It is also a large bone of the upper limb; the humerus articulates with the head of the radius at the elbow joint. It supports the thumb side of the forearm. There are two radius bones, one on each hand
(3)  Ulna: A long bone found in the forearm connects firmly to the humerus. According to the anatomical position, it is present on the medial side of the forearm. It runs parallel to the radius in the forearm. There are two ulna, i.e. one on each hand.
(4) Carpals or Wrist bones: They are sixteen small bones, i.e. eight in each hand which makes the wrist and connects the hand to the forearm.
(5) Metacarpals or Palm bones: These are present between the phalanges of fingers and carpal bones. They are ten small bones, i.e. five in each hand, consisting of a shaft, distal head, and a broad proximal base.
(6) Phalanges or Digits: They are the bones of the hand’s fingers.. There are three phalanges in each finger, excluding the thumb, two phalanges. Thus, the total number of phalanges in the upper limb is \(28\) (\(14\) in each arm).

1. Bones of Forelimbs:

Figure: The Upper Limbs

4. The Lower limbs or hind arm: The lower limb contains a total of \(60\) bones, i.e., \(30\) on each side. The lower limb consists of the following bones: femur, tibia, fibula, patella, tarsals, metatarsals, and phalanges.
(1) Femur: It is the longest bone of the body and the only bone in the thigh. It is present in the lower limb between the hip and the knee joint. There are two femurs, i.e. one on each leg
(2) Tibia: It is the second-largest and strongest bone of the body. It is also the main weight-bearing bone of the body. It articulates at the knee and ankle joints, respectively. There are two tibia, i.e. one on each leg
(3) Fibula: It is shorter and thin and attaches muscles of feet and toes It is lateral to tibia. There are two fibula, i.e. one on each leg
(4) Patella: This bone is also known as the kneecap. It is present at the literal side of the tibia. There are two patella, i.e. one on each leg. These are sesamoid bones.
(5) Tarsals are present in the ankle area; there are fourteen tarsal bones, i.e. seven in each leg. 
(6) Metatarsals: They are located between the tarsals bones of the hind and midfoot and are articulate with toes. There are ten tarsal bones, i.e. five in each leg.
(7) Phalanges: They are the bones of the toes of the leg. There are three phalanges in each toe, excluding the thumb, two phalanges. Thus, the total number of phalanges in the lower limb is \(28\) (\(14\) in each arm).

1. Bones of Hind Limbs:

Figure: The Lower Limbs

Appendicular Skeleton Function

The functions of the appendicular skeleton are:

Difference between Axial and Appendicular Skeletons

Summary

The appendicular skeleton keeps a human body in motion and helps in perform daily activities. This part of the skeleton system comprises of bones of the upper limbs (movement of forearms and shoulders), lower limbs (helps in motion), pectoral girdle (support the upper limbs), pelvic girdle (protect the vital organs of the abdominal cavity and transfer the weight to the lower limbs).

FAQs

Q.1: Which is the longest bone of our body?
Ans: Femur or thigh bone is the longest bone of our body.

Q.2: What are the functions of the axial skeleton?
Ans: The axial skeleton provides support and protection for the brain, spinal cord, and the organs in the ventral body cavity.

Q.3: What is the role of the appendicular skeleton?
Ans: The appendicular skeleton supports the attachment and functions of the upper and lower limbs of the human body.

Q.4: What is the appendicular and axial skeleton?
Ans: Appendicular skeleton-The appendicular skeleton includes all the bones that form the upper and lower limbs, the pelvic girdle, and the pectoral girdle. It consists of \(126\) bones.
Axial skeleton–The axial skeleton is the part of the skeleton that consists of the bones of the skull, the vertebral column, and the thoracic cage. It consists of \(80\) bones.

Q.5: What part is made on the appendicular skeleton?
Ans: The appendicular skeleton consists of the bones of the upper and lower limbs, the pelvic girdle, and the pectoral girdle.

Q.6: Name any \(8\) appendicular bones?
Ans: The \(8\) appendicular bones are Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges, Femur and Tibia.

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