The skeletal system is divided into two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton includes the skull, vertebral column, and rib cage, while the appendicular skeleton includes the bones of the upper and lower limbs, the girdles that attach the limbs to the axial skeleton, and the pelvis. In this article, we will explore the bones of the appendicular skeleton in detail.
The Bones of the Upper Limbs
The bones of the upper limbs consist of the humerus, ulna, radius, carpals, metacarpals, and phalanges. Let’s take a closer look at each of these bones:
The Humerus
The humerus is the long bone in the upper arm that extends from the shoulder to the elbow. It is the largest and strongest bone in the upper limb and supports the weight of the arm. It is also an attachment site for several muscles and ligaments.
The Ulna
The ulna is a long bone in the forearm that runs parallel to the radius. It is located on the side of the forearm opposite the thumb and is slightly longer than the radius. The ulna helps to form the elbow joint with the humerus and also provides attachment points for muscles and ligaments.
The Radius
The radius is a long bone in the forearm that runs parallel to the ulna. It is located on the side of the forearm that includes the thumb and is slightly shorter than the ulna. The radius helps to form the elbow joint with the humerus and also provides attachment points for muscles and ligaments.
The Carpals
The carpals are a group of eight small bones located in the wrist. They are arranged in two rows and provide flexibility and stability to the wrist joint. Each carpal bone has a specific shape and function.
The Metacarpals
The metacarpals are the five long bones located in the palm of the hand. They connect the carpals to the phalanges and provide structure and support to the hand. Each metacarpal bone is numbered from I to V, starting with the thumb.
The Phalanges
The phalanges are the bones in the fingers and thumb. Each finger has three phalanges, while the thumb has two. The phalanges are numbered from proximal to distal, with the proximal phalanx closest to the palm of the hand and the distal phalanx closest to the fingertip.
The Bones of the Lower Limbs
The bones of the lower limbs consist of the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges. Let’s take a closer look at each of these bones:
The Femur
The femur is the long bone in the thigh that extends from the hip to the knee. It is the largest and strongest bone in the body and supports the weight of the body. It is also an attachment site for several muscles and ligaments.
The Patella
The patella, also known as the kneecap, is a small bone located in front of the knee joint. It provides protection to the knee joint and improves the leverage of the quadriceps muscle during extension of the knee.
The Tibia
The tibia is a long bone in the lower leg that is located on the medial side. It is larger and stronger than the fibula and helps to support the weight of the body. It is also an attachment site for several muscles and ligaments.
The Fibula
The fibula is a long bone in the lower leg that is located on the lateral side. It is smaller and weaker than the tibia and provides attachment points for muscles and ligaments. It also helps to stabilize the ankle joint.
The Tarsals
The tarsals are a group of seven small bones located in the ankle. They are arranged in two rows and provide flexibility and stability to the ankle joint. Each tarsal bone has a specific shape and function.
The Metatarsals
The metatarsals are the five long bones located in the foot. They connect the tarsals to the phalanges and provide structure and support to the foot. Each metatarsal bone is numbered from I to V, starting with the big toe.
The Phalanges
The phalanges are the bones in the toes. Each toe has three phalanges, except for the big toe, which has two. The phalanges are numbered from proximal to distal, with the proximal phalanx closest to the foot and the distal phalanx closest to the toenail.
The Girdles of the Appendicular Skeleton
The girdles of the appendicular skeleton include the pectoral girdle and the pelvic girdle. These girdles attach the upper and lower limbs to the axial skeleton and provide support and stability to the body.
The Pectoral Girdle
The pectoral girdle, also known as the shoulder girdle, consists of the clavicle and scapula. The clavicle is a long, S-shaped bone that runs horizontally across the upper part of the chest. It connects the sternum to the scapula and helps to anchor the arm to the body. The scapula is a flat, triangular bone located on the back of the shoulder. It provides attachment points for several muscles and ligaments and also forms the shoulder joint with the humerus.
The Pelvic Girdle
The pelvic girdle, also known as the hip girdle, consists of the hip bones, sacrum, and coccyx. The hip bones, also called the innominate bones or os coxae, are large, irregularly shaped bones that make up the hips. They are attached to the sacrum and coccyx at the back of the pelvis and provide attachment points for several muscles and ligaments. The pelvic girdle also protects the organs in the pelvic cavity and provides support and stability to the body.
Common Questions and Answers
- What bones are part of the appendicular skeleton?
- The bones of the upper limbs, lower limbs, and girdles that attach the limbs to the axial skeleton are part of the appendicular skeleton.
- How many bones are in the appendicular skeleton?
- There are 126 bones in the appendicular skeleton.
- What is the function of the appendicular skeleton?
- The appendicular skeleton provides support and mobility to the body and helps to protect the organs in the thorax and abdomen.
- What is the largest bone in the body?
- The femur is the largest bone in the body.
References
1. Tortora, G. J., Derrickson, B. H. (2017). Principles of Anatomy and Physiology. John Wiley & Sons.
2. Moore, K. L., Dalley, A. F., Agur, A. M. R. (2018). Clinically Oriented Anatomy. Wolters Kluwer.
3. Saladin, K. (2015). Anatomy and Physiology: The Unity of Form and Function. McGraw-Hill.