The Four Types of Bone (2023)

The skeleton is the body's frame. It provides the foundation to which other structures cling and helps to create our shape. All 206 of the bones of the skeleton can be categorized into four types: long, short, flat, and irregular. Each type of bone serves a particular purpose and some types have more than one function.

The Four Types of Bone (1)

Long Bones

The skeleton of the arms and legs are made up of mostly long bones. Long bones are so-called because they are longer than they are wide. Long bones in the arm include the humerus, radius, ulna, metacarpals, and phalanges. Long bones of the leg include the femur, tibia, fibula, metatarsals, and phalanges. The clavicles (collar bones) are also long bones.

Long bones provide the leverage we need for moving our bodies and for manipulating our environment. All long bones have two main parts: diaphysis and epiphysis.


The diaphysis is the shaft of the long bone, the main body. The diaphysis is a tube with a hollow center called the medullary cavity (or marrow cavity). The wall of the diaphysis is made up of compact bone, which is dense and very hard. For most of the life of a long bone, the center of the diaphysis is filled with yellow bone marrow. Yellow bone marrow is basically fat, also known as adipose tissue.


Each end of a long bone is called an epiphysis. Each epiphysis is shaped to fit its connecting bone at a junction that is called a joint and the shape of the epiphysis is based on the job of the joint. The proximal (closer to the body) epiphysis of the humerus and the proximal epiphysis of the femur are shaped in a rounded manner, called the head, and look a bit like half of a ball. This shape allows those two long bones to rotate in multiple directions. The head of the femur fits into a socket in the pelvis. The head of the humerus fits into a socket in the shoulder. That type of joint is called a ball-and-socket joint. Joints that only allow movement along one axis are called hinge joints.

The wall of the epiphysis is made of compact bone like the diaphysis and the center contains spongy bone. Spongy bone is made of many small cavities (also called medullary cavities) filled with red bone marrow. Red bone marrow manufactures red blood cells and is very well connected to the circulatory system. There is so much blood flow through the spongy bone, that needles inserted into the spongy bone of the humerus, of the femur, or of the sternum (not a long bone as you'll see below) can be used to administer fluid or medications just like an intravenous line.

Epiphyseal Plate

There is a line that can be seen on images of the epiphysis and is called the epiphyseal plate. That is where new bone is added to increase the length of the long bone during development (called ossification). It is commonly known as the growth plate. Fractures (breaks and cracks in the bone) that include the epiphyseal plate can interrupt proper bone development in kids.

Short Bones

Short bones are called that because they about as wide as they are long. There is no diaphysis on a short bone. It is made up of spongy bone surrounded by compact bone just like the epiphysis. Short bones also contain red bone marrow.

There are 32 short bones in the human skeleton. Typically, short bones facilitate movement and strength in the complex joints of the wrist and ankles by sliding and shifting against each other.

The carpals (wrist bones), tarsals (ankle and heel bones), and the patella (kneecap) are all short bones. Some experts consider the patella a sesamoid bone (discussed below) because it primarily provides an anchor point for tendons and ligaments. However, the patella is common to everyone while sesamoid bones develop differently between individual people.

Flat Bones

Flat bones are the armor of the body. Flat bones provide structure, such as the shape of the head and torso, and the foundation of the shoulder and hip. Flat bones can also provide protection of soft tissues underneath. Like short bones, flat bones have walls that are made of compact bone and a center of spongy bone (with red bone marrow) that forms something like a sandwich.

The cranial bones, scapula (shoulder blade), sternum (breast bone), ribs, and iliac bone (hip) are all flat bones. Of these, the scapula, sternum, ribs, and iliac bone all provide strong insertion points for tendons and muscles.


The bones of the cranium are the part of the skull that encapsulates the brain. The bones of the cranium are connected together through joints called sutures, which look like they are stitched. Sometimes, additional small bones can develop between sutured bones of the cranium along the suture lines. These small bones are called sutural bones. They develop randomly and are not named bones.

(Video) Three Types of Bone Cells

Irregular Bones

Bones that are neither long, short, nor flat are considered irregular bones. The shapes of these bones provide very specific functions. The facial bones and the bones of the spinal column, the vertebrae, are all irregular bones. These bones have complicated shapes that are unique to their function. Most of the irregular bones appear only once in the body along the midline, such as each of the vertebrae. Some of the bones of the face appear in mirror image, such as the zygomatic bones (cheekbones).

Irregular bones often have complicated shapes that are used as insertion points for muscles, tendons, and ligaments. The most common shape is called a process that looks like a protrusion. The vertebrae each have three processes: the spinous process along the posterior (back) in the center (midline), and transverse processes on either side of the spinous process.

Sesamoid Bones

Sometimes, bones will develop due to friction along tendons or ligaments. Usually, these are very small bones and develop randomly between individuals. They are not named. Some anatomists consider the patella an example of sesamoid bone.

Frequently Asked Questions

  • How many bones are in the human body?

    There are 206 bones in the human body.

  • What is compact bone?

    Compact bone is the middle of three main layers in every bone. Its material is hard and smooth to protect bones and offer structural support. The outer layer is called periosteum, and the inner layer is known as spongy bone.

  • What are bones made of?

    Bones are made of collagen and calcium phosphate. Collagen is a protein involved in skin, hair, and nail health that is also found in muscles, bones, and tendons. Calcium phosphate is a mineral that gives bones strength.

  • What is the strongest bone in the body?

    The strongest bone in the body is the femur, or your thighbone. It is also the longest bone in the human body.

  • How many bones are in your hand?

    There are a total of 27 bones in the hand. This includes 14 phalanges (finger bones), five metacarpal bones, and eight carpal bones.

  • What is the diaphysis?

    The diaphysis is a tube-like structure that makes up the main shaft of a long bone. Its walls are made of compact bone, meaning it is hard and dense. Its center is filled with yellow bone marrow for most of the long bone's life.

2 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Maffei FA. Intraosseous cannulation. Medscape.

  2. Cepela DJ, Tartaglione JP, Dooley TP, Patel PN.Classifications in brief: Salter-Harris classification of pediatric physeal fractures.Clin Orthop Relat Res. 2016;474(11):2531-2537. doi:10.1007/s11999-016-4891-3

Additional Reading

(Video) Bone Cells

The Four Types of Bone (2)

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.

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What are the different types of bones questions and answers? ›

There are four major types of bones found in the human body (long, short, flat, and irregular), with two minor types of bones (sesamoid and sutural bones).

What are the four bone classifications based on shape give an example of each? ›

Long bones, such as the femur, are longer than they are wide. Short bones, such as the carpals, are approximately equal in length, width, and thickness. Flat bones are thin, but are often curved, such as the ribs. Irregular bones such as those of the face have no characteristic shape.

What are the four types of bone cells quizlet? ›

Terms in this set (4)
  • Osteogenic cells. *Derived from mesenchyme. *only bone cells to go under cell division. ...
  • Osteoblast. *bone building cells. *synthesizes and secretes collagen fibers and other organic components needed to build extracellular matrix of bone tissue. ...
  • Osteocytes. *Mature bone cells. ...
  • Osteoclast. *Huge cells.

What are four main functions of bones quizlet? ›

  • support and protect.
  • Body movement.
  • blood cell formation.
  • storage of inorganic salts.

What are bones made up of? ›

Bones are made up of a framework of a protein called collagen, with a mineral called calcium phosphate that makes the framework hard and strong. Bones store calcium and release some into the bloodstream when it's needed by other parts of the body.

How many bones are in the body? ›

There are typically around 270 bones in human infants, which fuse to become 206 to 213 bones in the human adult. The reason for the variability in the number of bones is because some humans may have a varying number of ribs, vertebrae, and digits.

What are the types of bones please explain with examples? ›

DefinitionBone is a living, rigid tissue of the human body that makes up the body's skeletal system.
Types of bonesFlat bones (e.g. skull bones) Long bones (e.g. femur) Short bones (e.g. carpal bones) Irregular bones (e.g. vertebrae) Sesamoid bones (e.g. patella)
4 more rows

What are some questions about bones? ›

Spinal and Skeletal Bone: Questions and Answers
  • How many bones are in the human body? An average adult has 206 bones. ...
  • How many bones are in the spine? There are 33. ...
  • How much do all the bones in the body weigh? ...
  • Are bones alive? ...
  • What is bone? ...
  • What is bone marrow? ...
  • Do bones have skin? ...
  • How does smoking affect the body?

What are the different types of bones test? ›

There are two main types of bone exams. A three-phase bone scan is a nuclear imaging test that shows how the bones process an injected agent. A DEXA bone scan is a type of X-ray that tests bone strength and density to diagnose osteoporosis.

How are bones classified give examples of each quizlet? ›

  • Long Bones. Long bones are so named because they are longer than they are wide. ...
  • Short Bones. Short bones are roughly cube shaped. ...
  • Flat Bones. Flat bones are thin, flattened and usually somewhat curved. ...
  • Irregular Bones. Irregular bones have various shapes that do not fit into the other categories of bone shapes.

What determines the classification of bones quizlet? ›

Bones can be classified according to their shapes. Long bones, such as the femur, are longer than they are wide. Short bones, such as the carpals, are approximately equal in length, width, and thickness. Flat bones are thin, but are often curved, such as the ribs.

How many types of bone formation are there? ›

There are two types of bone ossification, intramembranous and endochondral. Each of these processes begins with a mesenchymal tissue precursor, but how it transforms into bone differs.

Which of the following is not one of the four types of bones? ›

Of the above answer choices, the one that is not a type of bone is A. Round. An example of a flat bone is the sternum, an example of a long bone is the femur, and an example of a short bone is a carpal or tarsal.

What are the different types of bones how many types are there explain two different types of joints in our body? ›

The adult human skeletal system has a complex architecture that includes 206 named bones connected by cartilage, tendons, ligaments, and three types of joints: synarthroses (immovable) amphiarthroses (slightly movable) diarthroses (freely movable)

What kind of bone is a rib? ›

Answer and Explanation: The ribs that make up the human rib cage are flat bones. Flat bones are often described as 'plates' of bone. The sternum, to which the ribs are attached, is also a flat bone.

What are the 4 groups of bones that form the appendicular skeleton? ›

The appendicular skeleton includes the bones of the shoulder girdle, the upper limbs, the pelvic girdle, and the lower limbs.

What are the two types of bone and what are their features quizlet? ›

Compact bone: hard, dense and strong. Gives strength. Outside of bone. Cancellous bone: Lighter, softer, not as strong.

What are the five types of bone quizlet? ›

Terms in this set (5)
  • Long Bones. These bones are longer than they are wide. ...
  • Short Bones. These are cube-like in appearance, being as long as they are wide. ...
  • Flat Bones. These are thin bones that function to protect the tissues and organs of the body. ...
  • Irregular Bones. These are irregular in shape. ...
  • Sesamoid Bone.

What are the 4 main functions of skeletal muscle? ›

The main functions of skeletal muscle are to contract to produce movement, sustain body posture and position, maintain body temperature, store nutrients, and stabilize joints.

What are the main functions of bone? ›

Bone provides shape and support for the body, as well as protection for some organs. Bone also serves as a storage site for minerals and provides the medium—marrow—for the development and storage of blood cells.

What are 5 important functions of bones? ›

Your bones serve five main functions in your body, including:
  • Supporting your body and helping you move. Your bones literally hold up your body and keep it from collapsing to the ground. ...
  • Protecting your internal organs. ...
  • Producing your blood cells. ...
  • Storing and releasing fat. ...
  • Storing and releasing minerals.
Nov 24, 2021

What 4 things are bones made? ›

Bone is composed of four different cell types; osteoblasts, osteocytes, osteoclasts and bone lining cells. Osteoblasts, bone lining cells and osteoclasts are present on bone surfaces and are derived from local mesenchymal cells called progenitor cells.

What type of tissue is bone? ›

Bone is made up of compact tissue (the hard, outer layer) and cancellous tissue (the spongy, inner layer that contains red marrow). Bone tissue is maintained by bone-forming cells called osteoblasts and cells that break down bone called osteoclasts.

What 4 materials are bones made of? ›

As described above, by volume, bone consists of 40% inorganic component (hydroxyapatite), 25% water and 35% organic component (proteins) [1,2,12]. 90% of the organic component are collagen type I and the remaining 10% noncollagenous proteins.

How many bones have a baby? ›

A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have. Some of a baby's bones are made entirely of a special material called cartilage (say: KAR-tel-ij). Other bones in a baby are partly made of cartilage.

How many bones does a 7 year old have? ›

There are three hundred bones in children. That changes as they reach adulthood.

What are the 6 types of bones? ›

There are six types of bones in the human body: long, short, flat, irregular, sesamoid and sutural.

What are the different types of bones and cartilage? ›

Bones are of two types: compact or spongy. Cartilage is of three types: Hyaline cartilage, fibrocartilage and elastic cartilage.

What are the two main types of bone and where are they found? ›

Compact (cortical) bone is a hard outer layer that is dense, strong, and durable. It makes up around 80% of adult bone mass and forms the outer layer of bone. Cancellous (trabecular or spongy) bone makes up the remaining 20% of bone and consists of a network of trabeculae, or rod-like, structures.

Why is it important to classify bones? ›

Why is it important to classify bones? - It is important to classify bones because each bone has a unique shape and function. Aside from length, what are some other common characteristics of a long bone? Are long bones typically associated with the axial or appendicular skeleton?

What are the 4 characteristics of bones? ›

The four principal types of bones are long, short, flat and irregular. Bones that are longer than they are wide are called long bones. They consist of a long shaft with two bulky ends or extremities.

What is the largest bone in the body? ›

Your femur is the largest bone in your body. Most adult femurs are around 18 inches long. The femur is also the strongest bone in your body. It can support as much as 30 times the weight of your body.

What is the smallest bone in your body? ›

The stapes is the body's smallest bone! Sometimes called the stirrup, this delicate bone works with two others in the ear to send sound vibrations into the inner ear.

What is bone quizlet? ›

Bones are composed of a variety of tissues including bone tissue, cartilage, dense connective tissue, blood, and nervous tissue. What are the functions of bones? They support and protect softer tissues, provide points of attachment for muscles, house blood-producing cells, and store inorganic cells.

What are the 3 bone cells? ›

There are three types of cells that contribute to bone homeostasis. Osteoblasts are bone-forming cell, osteoclasts resorb or break down bone, and osteocytes are mature bone cells.

How many bones are in the human body quiz? ›

Question: How many bones does an adult human have? Answer: An adult human has 206 bones.

What is the name of flat bone? ›

Flat bones are made up of a layer of spongy bone between two thin layers of compact bone. They have a flat shape, not rounded. Examples include the skull and rib bones.

What are the major types of joints? ›

Histologically the three joints in the body are fibrous, cartilaginous, and synovial. Functionally the three types of joints are synarthrosis (immovable), amphiarthrosis (slightly moveable), and diarthrosis (freely moveable).

Which is responsible for bone structure? ›

Osteoblasts are bone cells that are responsible for bone formation. Osteoblasts synthesize and secrete the organic part and inorganic part of the extracellular matrix of bone tissue, and collagen fibers. Osteoblasts become trapped in these secretions and differentiate into less active osteocytes.

What determines bone size? ›

In conclusion, BMD and bone size are determined by a complex combination of genetic, lifestyle, and nutritional factors. In our study height, weight, prior exercise and milk intake, smoking and caffeine intake were the most frequent and important predictors of bone mineral density and bone size in these fit young men.

What are the five bone classifications describe each and give an example? ›

How are they categorized? There are five types of bones in the skeleton: flat, long, short, irregular, and sesamoid.

What does bone formation depend on? ›

Bone growth depends on genetic and environmental factors, including hormonal effects, diet and mechanical factors.

What are the four 4 types of bone cells explain their function? ›

Bone is a mineralized connective tissue that exhibits four types of cells: osteoblasts, bone lining cells, osteocytes, and osteoclasts [1, 2]. Bone exerts important functions in the body, such as locomotion, support and protection of soft tissues, calcium and phosphate storage, and harboring of bone marrow [3, 4].

What are the stages of bone? ›

There are three stages of bone healing: the inflammatory, reparative, and remodeling stages.

What are the 7 types of bones? ›

The bones of the human skeleton are classified by their shape: long bones, short bones, flat bones, sutural bones, sesamoid bones, and irregular bones (Figure 1).

How many bone names are there? ›

The adult human skeleton usually consists of 206 named bones. These bones can be grouped in two divisions: axial skeleton and appendicular skeleton. The 80 bones of the axial skeleton form the vertical axis of the body. They include the bones of the head, vertebral column, ribs and breastbone or sternum.

What are the 4 largest bones in the human body? ›

The Top Ten: Longest Bones in the Human Body
RankBoneAvg. Inches
1.Femur (thighbone)19.9
2.Tibia (shinbone)16.9
3.Fibula (lower leg)15.9
4.Humerus (upper arm)14.4
6 more rows

What are the 3 types of bone cells? ›

There are three types of cells that contribute to bone homeostasis. Osteoblasts are bone-forming cell, osteoclasts resorb or break down bone, and osteocytes are mature bone cells.

What are the 206 bones called? ›

The axial skeleton, comprising the spine, chest and head, contains 80 bones. The appendicular skeleton, comprising the arms and legs, including the shoulder and pelvic girdles, contains 126 bones, bringing the total for the entire skeleton to 206 bones.

What are the 10 functions of bone? ›

Functions of bones
  • Bones provide shape to the body.
  • Bones act as a protection to internal organs like brain, heart, lungs etc..
  • Provides support to the body and anchors muscles.
  • Bones serve as storage space for minerals like calcium and phosphate.
  • Bones helps in facilitating body movements.
Feb 5, 2021

What are the 6 functions of bone? ›

The human skeleton serves six major functions: support, movement, protection, production of blood cells, storage of ions, and endocrine regulation. Bone, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton, the support structure of the body.

What is bone made of? ›

Bones are made up of a framework of a protein called collagen, with a mineral called calcium phosphate that makes the framework hard and strong. Bones store calcium and release some into the bloodstream when it's needed by other parts of the body.

What are bone cells called? ›

Bone is composed of four different cell types; osteoblasts, osteocytes, osteoclasts and bone lining cells. Osteoblasts, bone lining cells and osteoclasts are present on bone surfaces and are derived from local mesenchymal cells called progenitor cells.

What type of bone is ribs? ›

Answer and Explanation: The ribs that make up the human rib cage are flat bones. Flat bones are often described as 'plates' of bone. The sternum, to which the ribs are attached, is also a flat bone.


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