How are Forelimbs different from Hindlimbs in Humans? – (In Detail)
Here in this post we will talk dedicatedly about the forelimbs and hindlimbs of humans and the difference between them.
The forelimbs are different from hindlimbs of humans in a number of ways. As we use our forelimbs to grip, hold, and catch things, while we use our hindlimbs to walk, run, and paddle while swimming. Our forelimbs are part of the anterior portion of the body, while hindlimbs are part of the posterior portion of the body.
In very common language we often say that the bones of hand are called forelimbs and that of leg are called hindlimbs.
Anatomically, the part of the human body starting from the shoulders to the elbow to the wrist and fingers are considered forelimbs. And, the part of the human body starting from the buttocks to the thigh to the knee to the foot and toes are considered hindlimbs.
This post is all about the differences and relationships between the forelimbs and hindlimbs of humans.
Let’s know more about it. So, just keep reading…
How are Forelimbs different from Hind limbs in Humans?
1. Muscular Differences
⇾ FORELIMBS
In our hands, there are four types of muscles: Interossei (Dorsal and Palmar) Muscles, Hypothenar Muscles, Thenar Muscles, and Lubrical Muscles.
There are 4 dorsal and 3 palmar Interossei muscles present between the bones of our each hand.
Three muscles together constitute the Hypothenar Muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. These muscles together compose the side muscles of the small finger for each hand.
Three muscles together constitute the Thenar Muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. Thenar muscles are present at the base of the thumb.
There are four Lubrical muscles present on each of the hands. The lumbricals are four, small, worm-like muscles on each hand. These muscles remain associated with the fingers of each of the hands to aid in the finger movement.
Then in each of our Elbows, there are 3 types of muscles: Biceps, Brachialis, and Triceps.
The Bicep is a prominent muscle on the front side of the upper arm. The Brachialis muscles is a single large muscle that allows the elbow to bent.
The Tricep muscle is located at the back of the arm and helps in straightening of our elbow.
Then our Shoulder muscles include the Deltoid muscle, Infraspinatus muscle, Supraspinatus Muscle, Teres Major, Teres Minor, Subscapularis Muscle, Latissimus Dorsi Muscle, Pectoralis Major Muscles, and Coracobrachialis Muscle.
The wrist and forearms muscle includes Flexor Pollicis Longus muscle, Flexor Digitorium Profundus muscle, Flexor Digitorium Superficialis, Flexor Carpi Ulnaris, Brachioradialis, Flexor carpi radialis, Palmaris Longus muscle, Extensor Pollicis Brevis, Extensor Pollicis Longus, Extensor Carpi Radialis Brevis, Extensor Carpi Radialis Brevis Longus, Extensor carpi Ulnaris, Extensor Digitorum Communis, Extensor Digiti Minimi, Extensor Indicis Proprius, Supinator, Pronator Quadratus, Pronator Teres.
⇾ HINDLIMBS
The muscles of the human hindlimbs include all those muscles starting from the large strong muscles of the buttocks and legs to the tiny muscles of the feet and toes.
Basically, there are 51 well-known types of muscles that constitute the whole hindlimbs of humans including many other small minute muscles as well.
Now, it is to be noted here that the Hip portion of the hindlimb is composed of the highest numbers of muscles each categorized with its kind of movements just like Lateral rotation movement, Medial rotation, Extension, Flexion movement, Abduction movement, and Adduction movement.
The muscles of the thigh can be classified into three groups according to their location. These are so termed as anterior and posterior muscles and the adductors.
The muscles of the legs are attached to the foot and some of the toes muscles are unique of their kind. They based on location can be classified into an anterior and a posterior muscle group separated from each other.
2. Skeletal Differences
⇾ FORELIMBS
There are altogether 30 numbers of bones in each of the human forelimb. It is to be noted here that the bones of both forelimb and hindlimb along with the pectoral and pelvic girdles respectively constitute the portion of the appendicular skeleton.
Here, in the case of forelimbs, the bones are the humerus, radius, ulna, carpals (8 in number), metacarpals (5 in number), and phalanges (14 in number).
The humerus is the single long bone of the upper arm. While Radius and Ulna are the two bones of the forearm portion.
Carpels are known as the wrist bones, Metacarpals are the palm bones, while Phalanges are digit bones or you can say them the finger bones.
⇾ HINDLIMBS
In each of the human hindlimb, there are altogether 30 bones. The bones of the hind limb are the femur bone, tibia and fibula, tarsals (7 in number), metatarsals (5 in number), patella bone, and phalanges (14 in number).
The femur bone is the single long bone of the upper leg. While Tibia and Fibula are the two bones of the lower leg portion.
Tarsals are known as the ankle bones, Metatarsals make up the middle area of the foot, while Phalanges are digit bones or you can say them the finger bones that comprise the toes.
There is also the Patella bone that makes up the kneecap.So, this bone is also known as the Kneecap bone.
3. Neurological Differences
⇾ FORELIMBS
There are 6 nerve branches in each of our hands. These are: Supraclavicular nerves, Axillary nerve, Inferior lateral cutaneous nerve, Intercostobrachial nerve, Medial cutaneous nerve, and Posterior cutaneous nerve of the arm.
There are 3 nerves in each of our Forearms. These are: Lateral cutaneous nerve, Medial cutaneous nerve, and Posterior cutaneous nerve.
In each of our Hands, there are 3 different types of nerve. These are: Superficial branch of the radial nerve, the Median nerve, and the Superficial branch of the ulnar nerve.
⇾ HINDLIMBS
There are 8 nerves in the Pelvis and buttocks region of the human hindlimb. These are: Lateral cutaneous nerve of thigh, Lumboinguinal nerve, Ilioinguinal nerve, Medial cluneal nerves, Inferior cluneal nerves, Perforating cutaneous nerve, Superior cluneal nerves, Iliohypogastric nerve, and Subcostal nerve.
In the thigh portion, there are 3 nerves. These are: Anterior cutaneous branches of the femoral nerve, Cutaneous branch of the obturator nerve, and Posterior cutaneous nerve of thigh.
In each of our legs, there are 8 nerves present. These are: Common fibular nerve, Lateral sural cutaneous nerve, Saphenous nerve, a branch of the femoral nerve, Superficial fibular nerve, Medial dorsal cutaneous nerve, Sural nerve, and also Medial sural cutaneous nerve.
The nerves of the foot are of 5 types. These include the Deep fibular nerve, Tibial nerve, Medial calcaneal branches of the tibial nerve, Medial plantar nerve, and the Lateral plantar nerve (green).
4. Behavioural Differences
⇾ FORELIMBS
The way we use our forelimbs and hindlimbs differently also can bring light into the difference between the two.
We, humans, have the thumb, followed by the index finger, middle finger, ring finger, and little finger that can work together and help us to take hold of things around us.
We humans can use our hands for doing a lot of daily activities like writing, carrying, playing games, typing, touching, and a lot of other things.
Our arms that include the upper and the lower arm contain many strong and flexible muscles that co-ordinately function together to do a lot of functions like carrying, climbing, crawling, etc.
Our arm muscles also help us in the movement of our hands and fingers with direct connection to the finger muscles.
⇾ HINDLIMBS
Our hind limbs muscles are very strong and flexible, which aid us to provide support to our upper body, and also aid in doing a range of movements like running, walking, swimming, riding bicycle, and in doing million other activities.
It is all due to the help of our legs that in the various dynamic situations such as running, hopping or jumping we behave with ease and without being overwhelmed by the complicated task.
Our hindlimb’s intrinsic and extrinsic foot muscles have the capacity to act as dampers and motors, dissipating, and generating mechanical energy.
This helps us support our overall body weight along with giving the required energy for overcoming the friction between the foot and surface.
It is also the human foot that is often described for providing the ultimate spring-like elasticity and flexibility during running, hopping, and jumping.
5. Evolutionary Differences
⇾ FORELIMBS
We have started adapting the use of our hands about 60 to 70 million years ago.
Then slowly at about 7 to 8 million years ago, we had learned to use our hands to grip on stuff with the aid of a longer thumb and fingers in spite of using it for locomotion and have evolved to becoming bipedal about 1 to 3.5 million years ago.
The adaptation had started along with various neuronal changes in our ancestors’ brain along with various muscular differences in the muscles, bones, anatomy of the forelimbs, along with the relocation of the eyes to the front of the face.
The adaptation of our hand to grip and get hold of things had started due to the consequent adaptation of many small ancestors that once lived on the ground and later on got adapted to lead their life up in the tree canopy as their new home.
⇾ HINDLIMBS
Almost about 7 to 8 million years ago, our early ancestors have learned to use their forelimbs completely for gripping and catching things and they have also learned to climb trees.
But, also during that time (about 7 to 8 million years ago) they were also using both their forelimbs and hindlimbs for locomotion when on land.
By 5 million years ago, they became more able to walk on their two hindlimbs but were still quadrupeds, meaning that they were still using both their forelimbs and hindlimbs for locomotion when on land.
Then it was about 2 to 3.5 million years ago that we have adapted to becoming completely bipedal and learned to have an erect bipedal posture by making well-use of our two hindlimbs for locomotion.
Scientists say that it was just about 1.5 to 2 million years ago that we became completely well-adapted to having longer legs for walking and running and became strictly bipedal.
What actually is a Forelimb?
The part of the paired human limb that is comprised of the shoulder portion, hands, elbow, wrist, and forearms are together termed as the forelimbs. We have two forelimbs.
In simple words, a forelimb is an anterior limb on a terrestrial vertebrate’s body like in a human’s body.
Our forelimbs are pentadactyle limbs as we have 5 fingers (digits) attached to the wrist portion.
Taking about the skelatal system of the forelimbs as it is a significant point to be noted then we must learn that there are altogether 30 numbers of bones in each of the human forelimb.
The bones of the forelimbs are: Humerus, Radius, Ulna, Carpals (8 in number), Metacarpals (5 in number), and Phalanges (14 in number). You can read more about this in the skeletal differences mentioned above.
The forelimbs are actually shorter than the hindlimbs. And, it is also to be noted that all vertebrate forelimbs are homologous meaning that they all have evolved from the same structures.
What actually is a Hindlimb?
The part of the paired human limb that is comprised of the hip portion, thigh, knee, the region from the keen including the ankle, foot, and toes are together termed as the hindlimbs. We have two hindlimbs.
In simple words, a hindlimb is a posterior limb on a terrestrial vertebrate’s body like in a human’s body.
It is also called the back limb and it remains attached to the posterior end of a terrestrial tetrapod vertebrate’s torso right at the pelvic girdle portion.
Our hindlimbs are pentadactyle limbs as we have 5 fingers (digits) in the toe portion of the hindlimb.
Taking about the skelatal system of the forelimbs as it is a significant point to be noted then we must learn that there are altogether 30 numbers of bones in each of the human forelimb.
The bones of the hindlimbs are: femur bone, tibia, fibula, tarsals (7 in number), metatarsals (5 in number), patella bone, and phalanges (14 in number). You can read more about this in the skeletal differences mentioned above.
The hindlimbs are longer than the forelimbs and are much stronger than the forelimbs. With the hindlimbs having bones that are strong, robust, and longer than the bones present in the forelimbs.
What is the purpose of forelimbs and hindlimbs in humans?
We, humans, are adapted to be able to use our forelimbs to climb, catch and hold something, and in gripping the stuff we see around us. We also use our forelimbs while crawling to support the anterior portion of the body.
We use our hindlimbs for walking, running, and supporting the whole body while we are standing. Our hindlimbs have the strongest muscles and bones in the thigh and lower leg portion that help to support the whole body weight.
Both our hindlimbs and forelimbs genetically, physiologically, and anatomically differs a lot from each other showing its different way of functioning.
However, there are some common things that both hindlimbs and forelimbs share together that are the various relationships between the two.
So, keep reading we will know more about this.
Relationship between Forelimbs and Hindlimbs of Humans
The first relationship is that we as humans have limbs that act as our arms in the case of forelimbs, and legs in the case of hindlimbs.
Also that the human skeleton is made up of two parts which are the Axial Skeleton part and another one is the Appendicular Skeleton part. Here, it is to be noted that both our forelimbs and hinds are part of the Appendicular Skeleton.
We have two pairs of forelimbs and hindlimbs, meaning that we have two forelimbs in the anterior part of the body, and another two hindlimbs in the posterior part of our body.
Both forelimbs and hindlimbs have the same number of bones that is 30 in the each of the limb.
There is 1 bone in the upper arm which is Humerus bone, and also 1 bone in the upper leg which is Femur bone.
There are 2 bones in the forearm portion which are radius and ulna respectively, and also 2 bones in the leg portion which are Fibia and Tibula respectively.
Both forelimbs and hindlimbs are pentadactyle, meaning that all have 5 digits (fingers) each.
Both forelimbs and hindlimbs have 14 number of phalanges bones that make up the fingers or digits.
There are two girdles in our skeletal system. Our forelimbs and hindlimbs are attached to those girdles through ball and socket joints of the skeleton.
The only difference is that the forelimbs are attached to the pectoral girdle and hindlimbs are attached to the pelvic girdles respectively.
Key Differences between Forelimb and Hindlimb of Humans – (In tabular Format)
| No. | FORELIMBS OF HUMAN | HINDLIMBS OF HUMAN |
|---|---|---|
| 1. | It includes shoulder portion, elbow, forearms, wrist, and hands. | It includes hip portion, thigh, knee, lower leg, ankle, foot, and toes. |
| 2. | Situated in the anterior portion of the body. | Situated in the posterior portion of the body. |
| 3. | Forelimbs are paired appendages i.e we have 2 forelimbs. | Hindlimbs are also paired appendages i.e we have 2 hindlimbs. |
| 4. | There are 30 bones in each forelimb. | There are also 30 bones in each hindlimb. |
| 5. | The names of the forelimb bones are: humerus, radius, ulna, carpals, metacarpals, and phalanges. | The names of the hindlimb bones are: femur, tibia, fibula, tarsals, metatarsals, patella, and phalanges. |
| 6. | Forelimbs are joined to the Pectoral Girdle bone. | Hindlimbs are joined to the Pelvic Girdle bone. |
| 7. | Used to hold, carry, catch, and grip. | Used to walk, run, paddle, and support the whole body weight. |
| 8. | Forelimbs are shorter and weaker than hindlimbs. | Hindlimbs are longer, robust, and stronger than forelimbs. |