THE APPENDICULAR SKELETON - Skyline E-learning site

THE APPENDICULAR SKELETON. The human body is an intricate system of bones, muscles, and organs that work together to keep us alive and functional. One of the most important structures in the body is the skeleton, which provides support and protection to the soft tissues of the body. The skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton.

The axial skeleton consists of the bones that form the central axis of the body, including the skull, vertebral column, and rib cage. The appendicular skeleton, on the other hand, consists of the bones of the limbs and the girdles that attach the limbs to the axial skeleton. In this blog post, we will focus on the appendicular skeleton and its functions.

types of Appendicular skeleton

The appendicular skeleton is composed of 126 bones, which are divided into four major regions: the upper limbs, lower limbs, pectoral girdle, and pelvic girdle. The upper limbs include the arms, forearms, wrists, and hands, while the lower limbs include the thighs, legs, ankles, and feet. The pectoral girdle connects the upper limbs to the axial skeleton and consists of the clavicle and scapula bones. The pelvic girdle connects the lower limbs to the axial skeleton and consists of the hip bones.

importance of Appendicular skeleton

The appendicular skeleton plays several important roles in the body. First and foremost, it provides support and stability to the body, allowing us to stand upright and move around. The bones of the appendicular skeleton are designed to withstand the stresses and strains of daily life, and they are reinforced by strong ligaments and muscles.

In addition to providing support, the appendicular skeleton is also involved in the movement. The bones of the limbs act as levers, which are moved by muscles to produce movement. The joints of the limbs allow for a wide range of movement, including flexion, extension, abduction, adduction, and rotation.

Another important function of the appendicular skeleton is protection. The bones of the limbs provide protection to the soft tissues of the body, including the vital organs in the chest and abdomen. For example, the ribs protect the heart and lungs, while the bones of the pelvis protect the reproductive organs and bladder.

Finally, the appendicular skeleton is involved in the production of blood cells. The bone marrow, which is found in the centre of many of the bones of the appendicular skeleton, produces red blood cells, white blood cells, and platelets. These blood cells are essential for transporting oxygen and nutrients throughout the body, fighting infections, and clotting blood.

In conclusion, the appendicular skeleton is a complex and important part of the human body. It provides support, stability, and protection to the body, allows for movement, and is involved in the production of blood cells. Without the appendicular skeleton, we would not be able to stand, walk, run, or perform any of the other activities that are essential to our daily lives.

The appendicular skeleton is made up of girdles. That is the pectoral and pelvic girdle, as well as the bones of the limbs which comprise the forelimbs and hind limbs.
Here let’s look at the structure, formation, and functions of these groups of skeletal systems.

The human skeleton can be broadly classified into two main categories, the axial skeleton, and the appendicular skeleton. The axial skeleton consists of the skull, vertebral column, and rib cage. In contrast, the appendicular skeleton comprises the bones of the limbs, the pectoral girdle, and the pelvic girdle. In this article, we will focus on the appendicular skeleton.

The appendicular skeleton includes 126 bones in total. The bones of the upper limb include the clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, and phalanges. The bones of the lower limb include the femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges. The pelvic girdle consists of the two hip bones, and the pectoral girdle includes the two scapulae and two clavicles.

The main function of the appendicular skeleton is to facilitate movement and locomotion. The bones of the limbs, in particular, provide support for the body and enable the execution of various physical activities. The pectoral and pelvic girdles serve as attachment points for the limbs and provide support for the upper body.

Let’s take a closer look at the bones of the appendicular skeleton.

Upper Limb Bones: The clavicle is an S-shaped bone that connects the sternum to the scapula. It serves as a strut that holds the scapula and arms away from the thorax, allowing for a full range of motion.

The scapula, also known as the shoulder blade, is a flat, triangular bone located on the upper back. It articulates with the clavicle and humerus to form the shoulder joint.

The humerus is the long bone of the upper arm, which articulates with the scapula at the shoulder joint and the radius and ulna at the elbow joint.

The radius and ulna are the two bones of the forearm. The radius is the shorter of the two bones and runs parallel to the ulna. The ulna is the long bone and is located on the medial side of the forearm.

The carpals, metacarpals, and phalanges are the bones of the hand. The carpals are the eight small bones that make up the wrist, while the metacarpals form the palm of the hand. The phalanges are the bones of the fingers.

Lower Limb Bones: The femur is the largest and strongest bone in the body. It is the bone of the thigh, which articulates with the pelvis to form the hip joint and with the tibia and patella to form the knee joint.

The patella, or kneecap, is a small, triangular bone located in front of the knee joint. It articulates with the femur and protects the knee joint.

The tibia and fibula are the two bones of the lower leg. The tibia is the larger, weight-bearing bone located on the medial side of the leg, while the fibula is the smaller bone located on the lateral side of the leg.

The tarsals, metatarsals, and phalanges are the bones of the foot. The tarsals are the seven small bones that make up the ankle, while the metatarsals form the sole of the foot. The phalanges are the bones of the toes.

In conclusion, the appendicular skeleton plays a crucial role in facilitating movement and locomotion. The bones of the upper and lower limbs, as well as the pectoral and pelvic girdles, work together to provide support and mobility for the body. Understanding the structure and function of the appendicular skeleton is essential for healthcare

THE PECTORAL GIRDLES

The pectoral girdle is found in the or around the shoulder in man. It is made of two halves which are held by muscles. Each half of the girdle is made of three bones. These bones are

THE SCAPULA OR SHOULDER BLADE.
THE CLAVICLE OR COLLARBONE
CORACOID

IN MAMMALS, THE SCAPULA AND THE CORACOID ARE FUSED TOGETHER to form what is called SCAPULA CORACOID.
THE SCAPULA IS A FLAT TRIANGULAR BONE.

AT THE APEX IS A HOLLOW OR CAVITY CALLED A GLENOID CAVITY INTO WHICH THE HEAD OF THE HUMERUS FITS TO FORM THE SHOULD JOINT.
Above the glenoid cavity is a small hook-shaped bone called coracoid bone.

On the other surface of the scapula, there is a ridge or spine called the scapula spine. It runs down towards the glenoid cavity.
The scapula spine ends with two projections which are acromion and metacromion.
The acromion is shorter than the metacromion but the metacromion is larger.
The clavicle is a small rod bone attached to the ligament joining the sternum to the acromion of the scapula.
The pectoral girdle especially the surface of the scapula, the two processes and the spine are important for the attachment of muscles and ligaments. The pectoral girdle also provides support for the forelimbs.

THE PELVIC GIRDLE

The pelvic girdle is found in the region close to the waist in men. It consists of two halves which are joined to each other ventrally and to the sacrum dorsally. The fusion is called PUBIS SYMPHYSIS.
Each half is called INNOMINATE BONE
Each half is made up of three bones, which are
1. Ilium
2. Ischium
3. Pubis
At the top of it, all is the ilium which is the largest and longest of the three bones. At the lower end is the fused bones, ischium and pubis. The ischium and the pubis enclosed an opening or a hole called OBTURATOR FORAMEN.
It is through these holes that nerves, blood vessels and muscles pass through. So on the other surface of each half of the girdle where the three bones meet, there is a deep hollow or depression called ACETABULUM where the head of the femur of the hind limb fits in to form the hip-joint which is an example of a ball and socket joint

THE LIMBS

What is a limb? Where can the limb be found?
The limbs are made up of the forelimbs which are the bones of the hands and the hind limbs which are the bones of the legs.
The limbs of most vertebrates are built in the same way or process, and this is called PENTADACTYL LIMB—5-digit plan.

It is made up of a long bone which is followed by a pair of two long bones that lies side by side. The pair of these long bones is followed by a set of nine small bones which are arranged in three rows.
The nine small bones are followed by five digits. Each digit of the small bone is called a phalange. Here is a diagram of the phalanges of man

THE FORELIMBS

What are the forelimbs? Where can we find a forelimb?
So forelimbs of a typical mammal are made up of an upper arm bone, which is a long bone called the humerus. It has a pounding head which fits in

and articulates with the glenoid cavity of the scapula of the pectoral girdle of the shoulder joint.
The lower of the humerus is like a hinged pulley-like surface called TROCHLEA. At the trochlea, the humerus articulates with the ulna and radius to form the elbow joint.

The humerus is followed by the bones of the forearm. The forearm bones are the radius and ulna. The radius is a long bone. It lies in front of the ulna and is slightly curved.

The ulna is longer than the radius. The ulna has a cavity called the sigmoid cavity. The trochlea fits into this cavity. The ulna also projects backwards to form a projection called OLECRANON PROCESS

The radius/ulna bone is followed by the bones of the wrists which are made of nine small bones arranged in three rows. These bones are called CARPALS. In the forefront, the carpals articulate with the radius/ulna and distally with the bones of the digits.
The wrist bones are followed by the bones of the digits. The digit bones are five and they are called metacarpals.
In man, the metacarpals are called fingers, and they are also referred to as the phalanges.
In man, each digit has three phalanges with the exception of the thumb which has only two. In Rabbits, the phalanges end in claws

THE HIND LIMBS

The hind limbs of a typical mammal are made up of the thigh bone called the femur. The femur is the largest and strongest bone found in the body. It is rounded at the proximal end to form a head which fits into the acetabulum of the pelvic girdle to form a hip joint.
Very close to the end of the femur, there are three projections called TROCHANTERS. They are very important for the attachment of muscles. At the distal end of the femur, are two rounded heads called CONDYLES. They articulate with the TIBIA bone. In between the two condyles is a pulley-like hoof.

The shank is made up of two bones called TIBIA and FIBULA. The Tibia is longer and stronger than the Fibula. At the end or proximal there are two grooves into which the condyles of the femur fit in
The fibula is a small bone which lies outside the tibia. In front of this joint is a small round bone called the PATELLA or KNEE-CAP
The ankle is made up of six bones called tarsals. The inner tarsals project backwards to form the heel bone.
The foot of a rabbit is made up of four digits called METATARSALS. Each digit is made up of three phalanges.
Most mammals including man have five metatarsals.

THE

RIBS

The ribs of a typical vertebrate are long semi-circular rods connecting the thoracic vertebrae to the breastbone known as the sternum.
It is found in the chest region of mammals. There are twelve ribs found in humans while the rabbit has thirteen in number. The bony cage formed by the ribs protects vital organs like the lungs and heart.
It also assists in breathing

So a typical rib consists of a head, which fits in between successive thoracic vertebrae, secondly a neck and most importantly the SHAFT.

Each rib articulates with the thoracic vertebrae through two processes.
i.

The CAPITALUM

which articulates with facets of the two nearby vertebrae and
ii.

The TUBERCULUM

known as the tubercle articulates with the transverse process.

The first seven pairs of ribs are called the true ribs because they are connected directly with the sternum by costal cartilages. The next five pairs of ribs are called false ribs because the eighth, ninth and tenth pair have a common connection with the sternum, each being attached to the costal cartilages of the ribs above.
The eleventh and twelfth ribs are called FLOATING RIBS because they have a connection whatsoever with the sternum

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