Bones are the principal component of an animal’s skeleton. You will find different types of bones in a skeleton. In this article, I will discuss the different types of bones from animal skeleton with labeled diagrams.
Last few days ago, I got several inquiries on the classification of bones. It is essential and the basic needs for any anatomy learner who starts learning anatomy. I decided to write the complete guide on bones like long bones, short bones, irregular bones with examples and diagrams.
So, if you are new and start learning anatomy, then this article may be helpful for you. I will try to describe every single point of different types of bones based on origin.
Types of bones
Knowing the type of any bone might help you to describe that bone easily. According to the bone’s shape, size, and structure, they have been classified into several categories.
Different authors classified the bones into various subclasses. Here, I will enlist types of bones from the animal skeleton based on shape, size, and structure.
- #1. Long bones of animals
- #2. Short bones of animals
- #3. Irregular bones of animals
- #4. Flat bones of animals
- #5. Sesamoid bones of the skeleton
- #6. Visceral bones of few animals and
- #7. Pneumatic bones of birds
“You may find four main or six types of bones in some books of veterinary anatomy.”
Now, I will show you the identifying osteological features of these different types of bones with examples. I hope this guide will help you learn and identify the long bones, short bones, irregular bones, or flat bones from any animal’s skeleton.
Long bones of an animal
These are the long hollow cylindrical types of bones found in the limbs of animals. Long bone has a shaft or a body and has two different extremities. It enclosed the large medullary cavity. These types of bone ossify in the cartilaginous method (endochondral ossification). Long bones function mainly as levers and aid in support, locomotion, and prehension.
For your better understand, I will enlist the main osteological features of a long bone of the skeleton. I hope these features might help you to identify all the long bones from animal’s body.
- #1.Presence of hollow elongated or cylindrical shaft
- #2. It consists of two extremities – proximal and distal extremity
- #3. It contains a large medullary cavity
- #4. Usually occurs in the forelimb or hindlimb of animals.
Long bones examples
Just look at the forelimb of any animal’s skeleton; there, you will find the scapula, humerus, radius and ulna, carpals, metacarpals, and phalanges bones. Does the scapula meet the above osteological features? Your answer will be – no, but what about the humerus bone?
The humerus is a cylindrical or hollow elongated type of bone that contains a sizeable medullary cavity. Again, you will find two expanded extremities (proximal and distal extremity) on the humerus bone. And it is the bone of the forelimb. So, you may consider the humerus as a long bone. Other examples of long bones from the skeleton of animals.
#1. Humerus long bone
#2. Radius and ulna long bone
#3. Metacarpal long bone
#4. Femur long bone
#5. Tibia and fibula long bone and
#6. Metatarsal long bone
You may find two other different types when studying the long bones – modified long bones and miniature long bones. So, what are the modified long bones and miniature long bones?
The bone that doesn’t possess the large medullary cavity but meets the other features of a long bone is known as modified long bones. Generally, you will find modified long bones (clavicle) in dogs, cats, rabbits, and birds skeleton.
Some bones of animals meet the osteological features of long bones but small in size. You may consider these small bones as miniature long bones.
If you look at the metacarpal bones of a dog, you will find all the features of a long bone. But the metacarpal bones of dogs are small in size. These are the miniature long bones of dogs.
Flat types of bones
These are the thin irregular bony plates that expand in two dimensions. Flat bones are designed for enclosing different cavities like the cranial cavity or pelvic cavity. These flat bones consist of two layers of compact bones with intervening spongy bones and marrow.
What are the main functions of flat bones? Flat bone furnishes sufficient area for muscle attachment and protects the organs they cover.
So, if I summarize the osteological features of flat bones, then the following points may find –
- #1. Mainly occurs in the skull, shoulder, and pelvic girdle
- #2. It expands in two directions
- #3. Protect vital organs of the body and provide a large surface for muscle attachments.
- #4. It consists of two layers of compact bones
Okay, let’s find the flat types of bones from the animal skeleton.
Example of flat bones
Look at the scapula bone; it is a triangular type of bone that has two expanded ends. This bone provides a large surface for muscle attachment. So, the scapula is a flat type of bone in animals. The other examples of flat bones from the animal skeleton are given below.
#1. Scapula flat bone
#2. Skull bones like frontal, occipital. Temporal bones
#3. Pelvic bones like ilium, ischium and pubis bone.
Short types of bones
These are the small pieces of bone that have a smooth surface. Short types of bones possess somewhat similar dimensions in length, breadth, and thickness. They are mainly found in the complex joints of an animal’s body and usually have six surfaces. They are primarily composed of spongy substances with a thin layer of compact cortical bone.
The primary function of short bones is in absorbing concussion. So, the osteological features of a short bone are listed below.
- #1. The surface of the bones is smooth.
- #2. Approximately equal in all directions.
- #3. Present six surfaces
Examples of short bones
There are six short bones between radius, ulna, and metacarpal bones. These six short bones are arranged in two rows. You will find radial carpal, intermediate carpal, ulnar carpal, and accessory carpal bones in the proximal row. Again, the distal row consists of the second and third fused carpal bone and fourth carpal bone.
If you look at the radial carpal bone, you will find the following osteological features –
#1. Located medial aspect of the proximal row
#2. Possess six surfaces, and these surfaces are irregular
#3. Equal in length, breadth, and height
#4. Short types of bones.
So, you may consider this radial carpal as a short bone. The other examples of short bones are –
#1. All carpal bones – like radial, ulnar, intermediate, and accessory carpals
#2. Few tarsal bones like central and fourth fused tarsal bone, second and third fused tarsal bones.
#3. Sesamoid bones like patella (I will discuss sesamoid bones separately).
Irregular bones of the skeleton
These are also the tiny types of bones that have rough and irregular surfaces. They are unpaired bones and are found in the midline of the skeleton. These irregular bones have different projections that help in the different types of muscles.
The irregular bones also consist of spongy substances with a thin covering of compact substances. So, the main osteological features of the irregular bones of the skeleton are –
- #1. They are in the median and unpaired bones
- #2. Having irregular shape and rough surfaces
- #3. Their projections help the attachment of muscles.
Examples of irregular types of bones
What are the irregular bones in an animal’s skeleton? Well, look at the axial skeleton of an animal. Is there any irregular types of bone in the skull? Probably, your answer will – no. So, what about in the vertebral column?
The first thoracic vertebrae of an animal is an unpaired bone and located in the midline of the skeleton. The surface of this first thoracic vertebrae is irregular and rough. You will find three prominent projections that help to attach muscle tightly. So, the thoracic vertebra is a irregular type of bone.
The other examples of irregular bones from the animal skeleton are –
#1. Cervical vertebrae,
#2. Thoracic vertebrae,
#3. Lumbar vertebrae
Features of pneumatic bone
Some bones have a cavity inside their bone body that accommodates air sac through pneumatic foramen in living conditions. These are the pneumatic types of bones of animals or birds. In the long bone of birds, there are some cavities inside their bodies that accommodates the air sacs. In mammals, a bone locates near the nasal cavity that contains air-filled cavities. These bones are also considered as pneumatic bones of mammals.
The best examples of pneumatic bones are –
- #1. Long bones of birds (like humerus of birds)
- #2. The frontal bone of mammals
- #3. Maxilla and premaxilla bones of mammals
Sesamoid types of bones
These are the small sesame seed types of bones that develop in the capsule of some joint or in a tendon. They work as pully to avoid friction.
The main functions of sesamoid bones in the body –
#1. It helps to diminish the friction
#2. Changes direction of tendons
#3. Increase leverage to muscles and tendons.
The patella is the most prominent sesamoid bone in the animal’s body. Another name of the patella is knee cap.
Visceral bones
These are the tiny bones found in the viscera of some animals and birds. There is a bone found in the pe-inis of a dog (os pen-eis of dog). You may discover visceral bones in different animals and birds. I am going to enlist the visceral bones from animals and birds.
#1. Ossa rostrale of pig is the small flat bony structure embedded within the rostral aspect of the nasal septal cartilage in a pig.
#2. Ossa cordis of cow – these are two small triangular bones embedded in the myocardium on either aspect of the aortic ring of cow’s heart. You will also find the ossa cordis in the heart of a horse.
#3. The Ossa pen-eis of a dog is an elongated bone located in the corpus cavernosum pen-eeis muscle at the cranial part of the dog’s pen-eis.
#4. Ossa optics of birds – this is a thin and U-shaped bone located in the scleral cartilage of the cock’s eye. But not present in all cock’s eyes.
Types of bones labeled diagram
Now, I will show you all these types of bones in a single picture. I hope this labeled diagram might help you identify different bones from animal’s skeleton (more photos).
Sometimes you may face some problems with some osteological terms. I want to provide some information on osteological terms. If you are interested to learn the osteological terms from different bones, then you may continue.
Osteological terms
Following osteological terms will help you a lot in learning the osteological features of different bones of animals. Please read these well and try to understand the main theme. If you want, you may get help from the video to understand these terms.
Facet – it is a small articular surface. In thoracic vertebrae, there are four facets, two on either end of the body. These facest are for the articulation with the concerned Head of the ribs.
Fovea – it is an articular surface in the form of a tiny pit. If you look at the head of the femur, there is a slight depression at the middle, know as fovea capitis femoris.
Fossa – it is a depression that is moderately deep. In humerus you will find the radial fossa, olecranon fossa and posterior fossa.
Condyles – these are the knuckled-shaped paired articular surface. In the humerus, you will find the lateral and medial condyles.
Epcondyles – these are the small projection near the condyles. Again you will find some small points on the condyles of the humerus bone.
Trochlea – it is a pully-like grooved articular surface. In the distal end of the femur bone, there is a pully-like structure (trochlea).
Process – it is a large projection like the transverse process of vertebrae.
Spine – is the slender or pointed projection. You will find the spine in the lateral aspect of the scapula of animals.
Tuberosity – is the large round projection. In the proximal end of the humerus bone, you will find lateral and medial tuberosities (lateral tuberosity is larger and prominent).
Tubercle – is a small projection. You will find a fascial tubercle in the fascial bone of the ruminant.
Trochanter – is considerable prominence. In the proximal end of the femur bone, there is a greater trochanter.
Different types of bones in various segments of limbs
Now, I will show you the different types of bones from the various parts of animal’s limbs.
Bones from the different segments of the forelimb of animals –
- #1. Shoulder girdle or pectoral girdle – scapula (flat bone), clavicle modified long bone)
- #2. Arm or brachium region – the humerus (long bones)
- #3. Forearm or antebrachium region – radius and ulna (long bones)
- #4. Maneus region – carpals (short bones), metacarpals (long bones)
Bones from the different segments of the hindlimb of animals –
- #1. Pelvic girdle – ossa coxarum (ilium, ischium, and pubis bones; flat bone) and sacrum
- #2. Thigh region – the femur (long bone)
- #3. Leg region – tibia and fibula bones (long bones)
- #4. Pes region – tarsal bones (short bones) and metatarsal (lomg bones).
Please watch the video for other osteological terms.
Functions of bone
You may also like to read the functions of bones. I will enlist the significant roles of bone.
#1. Bone makes the foundation and the proper shape of the skeleton.
#2. It protects the soft organs and delicate tissue of the animal’s body.
#3. The bone acts as levers in the different articulation of the body and indirectly help in locomotion.
#4. It also helps in erythropoiesis and respiration.
#5. The bone acts as a storehouse of calcium and phosphorous.
Please try to add other different functions of bone. For that, you may follow the anatomy book.
Frequently asked questions on types of bones
In this part of this article, you will get more frequently asked questions on different types of bone. If you don’t find your desire question on bones, please let me know.
What are the main 4 types of bones?
The main 4 types of bones from the skeleton are – long bone, short bone, flat bone, and irregular bone.
- #1. Long bones like the femur
- #2. Short bones like carpal or tarsal
- #3. Flat bone-like frontal and ilium
- #4. Irregular bone-like vertebrae
What are the 6 types of bones?
If you asked the main 6 types of bones, then you may answer –
- #1. Type 1: long bone
- #2. Type 2: short bone
- #3. Type 3: flat bone
- #4. Type 4: irregular bone
- #5. Type 5: sesamoid bone and
- #6. Type 6: pneumatic bone
What is the classification of bone?
I have already classified different bones as long, short, irregular, flat, sesamoid, visceral, and pneumatic bones. Examples of these bones are also provided in the main article.
- #1. Long – humerus bone
- #2. Short–tarsal bone
- #3. Irregular bone – lumbar vertebrae
- #4. Flat bone – frontal bone of the skull
- #5. Sesamoid – patella bone
- #6. Visceral – ossa cordis of ox
- #7. Pneumatic – humerus of birds
What are the examples of irregular bones?
The irregular bone is irregular in shape and has rough surfaces. They are located in the midline of the body and unpaired bone. Example of some irregular bones –
- #1. Cervical vertebrae bone
- #2. All thoracic vertebrae bone
- #3. All lumbar vertebrae bones
- #4. Sacrum vertebrae bones
- #5. Coccygeal vertebrae bones
What are the 2 types of bone?
Histologically bone is made with two types of tissue – compact substances and spongy substances.
- #1. Compact bone is a dense and hard substance located at the external aspect of the bone and surrounds the spongy substances.
- #2. Spongy or cancellous bone – a large number of very small boney plates unite irregularly, enclosing a small marrow space.
Fine, if you want to know more about compact and spongy bone, you may read articles from the histology section.
What is the softest bone in the body?
The clavicle is the softest bone in the body. If you thin histologically, then the cancellous or spongy bone is the most delicate bone than compact bone. Do you know about the weakest bone of the body? Stapes is the weakest bone in the animal’s body.
What is an osteon?
The compact bone comprises a boney tissue that is arranged in a definite pattern known as osteon. The other name of osteon is the Haversian system. You will find different types of lamellae, Haversian canal, Volkmann’s canal in the Haversian system. If you want to know more about the Haversian system or osteon, you may read my complete guide here.
What are bone cavities called?
Bone cavities are known as medullar cavities or marrow cavities.
What is bone and its functions?
Bone is the most complex structure that helps to make the foundation and proper shape of the skeleton. The main functions of bones are –
#1. It supports and furnishes the soft organs of the body
#2. Indirectly helps in locomotion
#3. The pneumatic bone helps in flying
Which is the longest bone?
The bone of the thigh (femur) is the longest bone of animals. But it may vary in other animals or birds. In birds, the tibiotarsus is the longest bone.
What is the purpose of the long bones?
The long bone bears the weight of the body and indirectly helps in locomotion. You will find most of the long bones in the forelimbs and hindlimbs of the animal’s skeleton.
Conclusion
This is a short guide to learn different types of bones from animal skeleton. I will update this article regularly with more new bone-labeled diagrams in the future.
You might know the osteological features of different types of bone to identify them from an animal skeleton.
