SKULL BONES OR CRANIAL BONES - LESSON 208

Now in this lesson we are going to learn about Cranial Bones.

Cranial bones are the bones of the cranium. The other name of cranium is skull. These bones cover and safeguard the brain and the other structures related to the brain that are sense organs such as ears, eyes, nose, mouth and skin of the skull and face.

Cranial bones are connected with the muscles responsible for the movements of the head and chewing functions of the mouth. The cranial bones are attached to each other with a joint called sutures. When a baby borns the cranial bones are not connected completely but with gaps.

At birth, these gaps are filled with unossified tissues in the cranium. These gaps are called as soft spots and they are also known as fontanelles. These fontanelles resemble small fountains. Whenever we touch these areas, we can feel the blood vessels inside them and their pulsations.

Cranial bones are of six in types. They are as follows:

1. Frontal bone

2. Sphenoid bone

3. Occipital bone

4. Temporal bone

5. Parietal bone

6. Ethmoid bone

Now we will see about each bone one by one.

In the next post we will learn about each of these cranial bones one by one in detail.  Okay.

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BONE DEPRESSIONS - LESSON 207

BONE DEPRESSIONS: They are the hollow regions or the openings found in the bones.  The bone depressions attach the bone to the other bone.  They serve as the route or passageways for nerves and blood vessels.  There are five types of bone depressions.  They are fossa, sinus, sulcus, fissure, and foramen. Now will learn the types  of bone depressions one by one. 

1.  Fossa:  These are the bony depressions are shallow cavities.  They are found inside the bones or on the bones.

2.  Sinus:  These are the depression of the bone that are found within bone.  Sinuses are hollow cavities in strucutre.

3.  Sulcus:  These type of bony depressions look like grooves or furrow in structure.

4.  Fissure:  They are a kind of bony depressions that are found on the bone.  They are narrow in size.  Fissures are deep slit like openings are found on the bone.

5.  Foramen:  These type of bony depressions act as the openings for nerves and blood vessels. They are also found on the bone.

In the next lession we will learn about Cranial Bones.  Okay.

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HUMAN BONE PROCESSES - LESSON 203

In this lesson we are going to learn about Human Bone Processes

Human Bone Processes: These are the enlarged parts of the human bones. They extend out from each human bone. Tendons and muscles attach to them in the bones. Now we will see the types of bone process one by one. Each bone consists of the following processes in it. They are as follows:

1. Bone head

2. Condyle

3. Trochanter

4. Tubercle

5. Tuberosity.

1. Bone head:- This is a bony process found on each bone. This bony process is round in shape and it is a separated area from the bone body. Bone head is attached to the bone body by a neck-like groove called bone neck.

2. Condyle:- This bony process is rounded in shape. It looks like knuckle-like structure in the bone joint.

3. Trochanter:- This bony process attach muscles to the femur bone. The Trochanter is large in structure.

4. Tubercle:- This bony process is small and rounded in structure. Tubercle is found in many bones of the human body. Tubercle attaches muscles or tendons to the bone.

5. Tuberosity:- This bony process is large and rounded in structure and is found in many bones of the human body. Tuberosity attaches tendons or muscles to the bones.

In the next lesson we will learn about Bone Depressions.

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COMPACT BONE AND CANCELLOUS BONE - LESSON 202

In this lesson we will learn more about the structure of the bone about the two layers of the bone.  They are compact bone and cancellous bone.  Now we will about one bye one now. Okay.

Compact bone is also known as cortical bone is a layer of hard, dense tissue that lies under the periosteum in all bones and chiefly around the diaphysis of a along bones. The blood vessels are located within the compact bone which are the system of small canals that bring oxygen and nutrients to the bone and remove waste products such as carbondioxide. The haversian canals are located in the compact bone. The compact bone is tunneled out in the shaft of the long bones by a central medullary cavity which contains yellow bone marrow. This yellow bone marrow is chiefly composed of fat cells.

Trabecular bone or spongy bone or cancellous bone:  This bone is to a great extent less dense and more porous comparing the compact or cortical bone.  This is made up of trabeculae or a spongy latticework.  This is found mostly in the epiphysis regions of the long bone and also in the central segment of the most bones of the body.  Red bone marrow is the thing that fills the spaces in the cancellous bone.  Comparing yellow marrow in compact bone, red marrow is supplied with blood and this is a fatty tissue matter.  Red bone marrow consists of both mature and immature blood cells in different phases of growth.  In the bones of the ribs, sternum or breastbone, pelvic bone, and vertebrae bones, and also in the epiphyses of the long bones, red bone marrow is filled within the cancellous tissue.  But red bone marrow is abundant in young children than the adults.  The amount of red bone marrow decreases when the young children become adults and this is replaced by the yellow bone marrow.

In the next lesson we will learn about the Bone Processes.  Okay.

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HUMAN BONE STRUCTURE II - LESSON 201

Now in this lesson we will try to learn about the remaining part of structure of the bone.

The long, relatively straight main body of a long bone, region of primary ossification which is also known as the shaft or middle region of a long bone is called the diaphysis. The end of a each long bone or the regions of secondary ossification is called an epiphysis. The epiphyseal plate is also known as the growth plate or physis. This plate represents an area of cartilage tissue that is constantly being replaced by new bony tissue as the bone grows. 

In a long bone, it is a thin disc of hyaline cartilage that is located transversely between the epiphysis and metaphysis. In the long bones of humans, the epiphyseal plate disappears by the age of twenty. The new bone that is responsible for the lengthening of bones during childhood and adolescence if formed by the cartilage cells at the edges of the epiphyseal plate. When the bone achieved its full growth, the plate calcifies and disappears.

The proximal articular end of the bone is called head. The region of bone between the head the shaft is called neck. 

The periosteum is a strong, fibrous, vascular membrane which covers the surface of a long bone, except at the ends of the epiphyses. Bones other than long bones are completely covered by the periosteum. Beneath the periosteum is the layer of osteoblasts, which deposit calcium phosphate in the bony tissue.

The ends of long bones are covered by a thin layer of cartilage called articular cartilage. This cartilage layer cushions the bones at the place where they meet with other bones joints.

Compact bone is also known as cortical bone is a layer of hard, dense tissue that lies under the periosteum in all bones and chiefly around the diaphysis of a along bones. The blood vessels are located within the compact bone which are the system of small canals that bring oxygen and nutrients to the bone and remove waste products such as carbondioxide. The haversian canals are located in the compact bone. The compact bone is tunneled out in the shaft of the long bones by a central medullary cavity which contains yellow bone marrow. This yellow bone marrow is chiefly composed of fat cells.

In the next post we would try to learn about cancellous bone and the remaining.

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HUMAN BONE STRUCTURE - LESSON 200

Now in this post we will learn about the structure of the bone. In our human body there are 206 bones of different types are there. The thigh, lower leg, and upper and lower arm consists of long bones. These bones have large surface areas for muscle attachment and are very strong, are broad at the ends where they join with other bones.

There are five types of bones in the human body. The five types are long, short, flat, irregular, and sesamoid.

1. Long bones:- These bones are comprised mostly of compact bone and lower amounts marrow, which is located within the medullary cavity, and spongy bone and are characterized by a shaft, the diaphysis, that is much larger in length than breadth. These bones are mostly present in the limbs, including those of the fingers and toes are long bones. Except the wrist, ankle, and kneecap these long bones are located in most.

2. Short bones:- These short bones are generally cube shaped and having a thin layer of compact bone surrounding a spongy interior. These short bones are found in the wrist and ankle and have small, irregular shapes.
3. Flat bones:- These bones are thin and generally curved, with two parallel layers of compact bones which are sandwiching a layer of spongy bone. Larger number of bones of the skull are flat bones as is the sternum. These flat bones are covered with soft body parts. These are the shoulder bone, ribs, and pelvic bones.

4. Irregular bones:- These bones do not fit into the above various bones. They contains of thin layers of compact bone surrounding a spongy interior. According to the name itself their shapes are irregular and complicated. These bones are in the spine and hips.

5. Sesamoid bones:- These bones are small, rounded bones resembling a grain of sesame in shape. They are found near the joints. The best example of this types of bone are present in kneecap. Because these bones are embedded in tendons. They hold the tendon further away from the joint, the angle of the tendon is increased and thus the leverage of the muscle is increased. The best examples of these sesamoid bones are the patella and the pisform. 

In the next lesson we will learn about the remaining structure of the bone.

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AMYOTROPHIC LATERAL SCLEROSIS - AN EXPLANATION - LESSON 199

ALS is nothing but amyotrophic lateral sclerosis. The other name of this disease is Lou Gehrig's disease. Amyotrophy means muscle wasting caused by disease of the nerves that supply to the muscles.  The cause is unknown yet medically. A- means nothing, myo-means muscle, and -trophy means growth, sclerosis means hardening or thickening. That is a state in which muscle gets hardened or thickened due to no sensation.  

Our nervous system is of two types that is Central nervous system and peripheral nervous system (PNS).  Central nervous system includes brain and spinal cord and the nerves associated with it that is integrative and control centers of the body (central and autonomic nerves).  Peripheral nervous system consists of the cranial nerves (nerves that connect eyes, ears, nose, and mouth to the brain) and spinal nerves (nerves connect the brain to the hands and feet).  Peripheral nervous system is an extension of central nervous system, which unites CNS to the upper and lower extremities (hands and feet) and other organs in the body.  These two nervous systems coordinate all body functions in our body.   The functions of total nervous system are of two types that are motor and sensory, by which we connect ourselves internally and externally to the world.

Amyotrophic lateral sclerosis (ALS) is a neurological disease condition, in which the nerves interrupted or collapsed from doing their normal function i.e. nerve tissues in the CNS (Central Nervous System) are affected and degenerated. When this disease affects a person's body movements affect, as this ALS has an effect on the motor nerves in charge for the movements.

Now we will see the description of amyotrophic lateral sclerosis.   Body moves when the sensation from the upper motor neuron reaches the lower motor neurons through brain and spinal cord.  In amyotrophic lateral sclerosis (ALS), these motor neurons answerable to the muscle movement stop working the 'voluntary' muscles in the hands, the feet, and the body.  This condition of muscles is called amyotrophy.  In this state the other sensations of the eyes, ears, nose, and mouth will not get affected, but only the muscle movements.

In the next post we will learn about STRUCTURE OF THE BONES..Okay..

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