Bones and Types of Bone

Olawunmi Omosanya - Tue, 02nd July, 2019 @ 17:31: PM

Topics in Biology

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Academic Questions in Biology

Chemical digestion of carbohydrate (cooked starch) begins in the _____.

  1. mouth
  2. oesophagus
  3. stomach
  4. small Intestine
  5. large Intestine

ANSWER is Mouth

The digestion of carbohydrate (cooked starch) begins in the mouth through an enzyme called salivary amylase (formerly called ptyalin) found in the saliva. This enzyme breaks down the starch present in carbohydrates into maltose. Maltose is a disaccharide. Please read on sugars and disaccharide here.

Note: With regards to digestion, chemical digestion is emphasized. We also have mechanical digestion which involves the grinding action of the teeth.



The bone is the major skeletal material present in the skeleton of vertebrates. A fully formed bone is composed of living cells called osteocytes (The osteocytes are arganic in nature). These bone cells  (osteocytes) are fortified or made strong by minerals (which are inorganic), especially hydroxyapatite (formed from calcium phosphate) and calcium carbonate. Collagen fibres are also present as a component of bones.The mineral component of the bone cells are non living and they account for about two third (2/3) of the mass of the bone. This is why a bone is much stronger and rigid than a cartilage (as a result of their high mineral content).

Note: Calcification of bones will only occur when collagen fibres are present.

Calcification is the process whereby mineral salts (hydroxyapatite) are deposited on the collagen fiber. This process crystallizes and hardens the bone tissue.

In general, we have 4 types of the cells that make up bones. These are:

1. Osteoblasts: These bone cells are responsible for bone formation. They secrete both the organic and inorganic components of the bone.

2. Osteocytes: These are matured bone cells and do not undergo division. They maintain the bone’s structure by recycling the mineral component of bone matrix. They are the living tissues in bone and make up about one third (1/3) of the mass of a matured bone.

3. Osteoclasts: They are large bone cells that function to dissolve (remove) the bone structure. They release lysosomal enzymes and acids on the bone matrix to bring about their dissolution effect. Through this process, calcium and phosphate minerals are released into the blood and body fluids in order to increase their concentrations. This process is important in certain physiological conditions.

4. Osteoprogenitor cells: They are responsible for the formation of osteoblasts which makes them important for the repair of broken bones (fracture).

Ossification is the natural process that leads to the formation of bone by osteoblasts. Another term for ossification is osteogenesis.


Types of Bone

Adult human beings have a total of 206 bones while a newly born child has even more. Knowledge of all the bones in the human body will help you better understand the human skeleton.

Please read on the 206 bones of the human body here.

You may also read on the amazing facts on biology here.


Bones can be classified based on a number of criteria. We will consider 4 of these:

  1. Classification of bone based on shape

We have 7 types of bones with regards to their shape. These are:

Image Credit: Owlcation


a. Long Bones

These bones appear long in appearance because they typically have an elongated shaft called diaphysis and two expanded ends on either side of the diaphysis. The expanded ends are referred to as the epiphysis. The epiphysis is covered with an articular cartilage because joints are formed around them. Within the shaft of long bones is a space or cavity called the medullary cavity.

The medullary cavity contains the bone marrow

Note: All blood cells are produced in the bone marrow. Blood cells include:

  • Red Blood Cells or Erythrocytes
  • White Blood Cells or Leukocytes
  • Platelets or Thrombocytes

Please read on Red Blood Cells here

We have three categories of long bones. These are:

  1. Elongated long bones: Examples are bone of the thigh (femur), bone of the arm (humerus), bone of the forearm (ulna and radius), bone of the leg (tibia and fibula).
  2. Miniature long bones: They are miniature in appearance and have only one epiphysis. Examples are the bones of the hands and foot (that is, metacarpals, metatarsals and phalanges).
  3. Modified long bones: These bones are modified in appearance as they have no medullary cavity. As a result, bone marrow is usually absent. The clavicle or collar bone is an example of modified long bone.


b. Short bones

They are short is appearance and are often named according to their respective shapes. The bones comprising the wrist and ankle (carpal and tarsal bones) are short bones.

Wrist bones (also known as the carpal bone) includes:

  • scaphoid bon
  • Lunate bone
  • Triquetral bone
  • Pisiform bone
  • Trapezium bone
  • Trapezoid bone
  • Capitate bone
  • Hamate bone

The ankle bones (also known as tarsal bone) are:

  • Calcaneus bone
  • Navicular bone
  • Talus
  • Medial Cunieform bone
  • Lateral Cunieform bone
  • Cuboid boid


c.  Sesamoid Bones

These bones look like the sesame seed and are embedded inside of joint capsules. They will usually develop inside a tendon, thus are usually present within joints. They will ossify only after birth. A typical example of a sesamoid bone is the patella found in the kneecap/knee joint.


d. Flat bones

They are thin and broad in appearance with two main surfaces. Their surfaces aid in the attachment of various muscles. The scapula, the bone that make up the roof of the skull, sternum (breast bone) and ribs are flat bones.


e. Irregular Bones

These bones have a variety of shape, hence the name “irregular bone”. They could be flat, short or notched in shape depending on their location. They are found in the pelvis, vertebrae and the base of the skull.


f. Pneumatic Bones

Although these bones are irregular in shape, they are also very light because of the presence of large air cavities or spaces within them. Examples are the maxilla, sphenoid and ethmoid bones which contribute to the lightness of the skull.


g. Sutural Bones
These bones are small and flat with irregular shapes. They are present as part of the skull bone.

Please read the classification of bones based on their structure, development and bodily region here

Amazing facts in Biology

An adult human being is composed of about 60% water. In fact, a newly born baby is composed of about 80% of water. This will drop to 65% after a year and finally to about 60% as the child ages

Without saliva, food can never be enjoyed. Food becomes tasteless since saliva is needed to dissolve the chemicals present in food onto the tongue’s taste buds.

Saliva also contains an enzyme called salivary amylase or "ptyalin" which helps to digest cooked starch to maltose. Maltose is a double sugar or disaccharide. Please read on sugars here


The gas used in the manufacture of food by plants is Carbon dioxide or Carbon(IV)oxide or CO2. 

Plants manufacture food through a process called photosynthesis. Please read on photosynthesis here

Note: Plants are the only orgnisms that take away CO2 from the atmosphere

In the Biological organization of life, it is said that cells form tissues, tissues form organs and organs form systems. There are 12 systems in the human body; these are:

  1. Cardiovascular System
  2. Digestive System
  3. Endocrine System
  4. Immune System
  5. Integumentary System
  6. Lymphatic System
  7. Muscular System
  8. Nervous System
  9. Reproductive system
  10. Respiratory System
  11. Skeletal System
  12. Urinary or Renal System

Please read on the amazing facts in Biology here

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