All questions of Skeletal System for Primary 6 Exam

Tendons connect muscles to bones. They are strong, flexible bands of tissue that transmit the force from muscles to bones, allowing us to move.

Hinge Joint: Movement in One Direction Only

A joint is a point where two or more bones come together. Joints allow movement and flexibility in the body. There are different types of joints in the body, each with its own range of motion and characteristics.

The joint that allows movement in one direction only is called a hinge joint. This type of joint resembles a hinge on a door and allows movement in a back-and-forth motion, similar to opening and closing a door. The hinge joint is found in various parts of the body, including the elbow and the knee.

Let's explore the characteristics and functions of a hinge joint in more detail:

1. Definition of a Hinge Joint:
- A hinge joint is a type of synovial joint, which means it is surrounded by a joint capsule filled with synovial fluid.
- This type of joint allows movement in only one plane, similar to the opening and closing of a hinged door.

2. Structure of a Hinge Joint:
- A hinge joint consists of two bones that articulate with each other.
- The ends of the bones are covered with smooth cartilage, which reduces friction and allows for smooth movement.
- Ligaments, which are tough bands of connective tissue, provide stability to the joint.

3. Function of a Hinge Joint:
- The primary function of a hinge joint is to allow movement in one direction only.
- The movement at a hinge joint is limited to flexion (bending) and extension (straightening).
- Examples of hinge joints in the body include the elbow joint and the knee joint.

4. Examples of Hinge Joints:
- Elbow Joint: The elbow joint is a hinge joint that allows for flexion and extension of the forearm. This joint enables movements like bending the arm and straightening it back.
- Knee Joint: The knee joint is another hinge joint that allows for flexion and extension of the leg. It enables movements like bending the leg and straightening it back.

In conclusion, a hinge joint is a type of joint that allows movement in one direction only. It resembles a hinge on a door and is found in joints like the elbow and knee. Understanding the different types of joints in the body helps us appreciate the complexity and functionality of our musculoskeletal system.

How to Have Strong Muscles
Maintaining strong muscles is essential for overall health and well-being. Here are some key ways to achieve strong muscles:

Regular Exercise
- Regular exercise, especially strength training exercises like weightlifting, resistance band workouts, and bodyweight exercises, helps to build and strengthen muscles.
- Engaging in activities like yoga, Pilates, and high-intensity interval training (HIIT) can also help improve muscle strength and endurance.

Proper Nutrition
- Consuming a balanced diet rich in protein, healthy fats, vitamins, and minerals is crucial for muscle growth and repair.
- Protein is particularly important for muscle building, as it provides the necessary amino acids for muscle synthesis.

Adequate Rest and Recovery
- Giving your muscles time to rest and recover is essential for muscle growth. Aim for 7-9 hours of quality sleep each night to allow your muscles to repair and rebuild.
- Incorporating rest days into your workout routine is also important to prevent overtraining and injury.

Hydration
- Staying hydrated is crucial for muscle function and recovery. Drink plenty of water throughout the day to support optimal muscle performance.

Consistency
- Consistency is key when it comes to building and maintaining strong muscles. Make exercise and proper nutrition a regular part of your lifestyle to see long-term results.
By following these guidelines and incorporating regular exercise, proper nutrition, rest, hydration, and consistency into your routine, you can build and maintain strong muscles for optimal health and fitness.

Fixed Bones in the Skull

The skull is made up of several bones that protect the brain and give shape to the head. While some of these bones are movable, others are fixed and do not have the ability to move. The fixed bones in the skull include:

1. Cranium:
The cranium is the upper part of the skull that encloses and protects the brain. It is composed of several bones that are fused together, forming a solid structure. The bones of the cranium include the frontal bone, parietal bones, temporal bones, occipital bone, sphenoid bone, and ethmoid bone. These bones are fixed and do not move.

Movable Bones in the Skull

While the cranium forms the fixed part of the skull, there are other bones in the skull that are movable. These include:

1. Lower Jaw:
The lower jaw, also known as the mandible, is the only movable bone in the skull. It is attached to the rest of the skull by a joint called the temporomandibular joint (TMJ). This allows for movements such as opening and closing the mouth, chewing, and speaking.

2. Nose:
The nose is made up of several bones, including the nasal bones and the vomer bone. Although the bones of the nose are not fixed in the skull, they are not considered movable bones either. The bones of the nose provide structure and support to the nasal cavity.

3. Cheekbones:
The cheekbones, also known as the zygomatic bones, are not fixed in the skull. They are located on either side of the face and contribute to the structure of the midface. The cheekbones are not directly attached to the rest of the skull but are connected to the maxilla bone.

In summary, the cranium is the only part of the skull that contains fixed bones. The lower jaw, nose, and cheekbones are not fixed in the skull and have some degree of mobility.

Muscles work by not pushing them, but by pulling them. If muscles worked by pushing our bones,  then our bones would have got dislocated every time we move. So the statement that muscles can push bones to make them move is completely False.

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The skull in the human body serves an essential function of protecting the brain. Below are some key points explaining the function of the skull:
- Protection of the Brain: The skull is a bony structure that encases and protects the brain from external injuries. It acts as a hard barrier that shields the delicate brain tissue from trauma, impacts, and potential damage.
- Support and Structure: The skull provides a framework for the face and head, giving shape, support, and structure to the facial features. It also houses and protects other vital organs such as the eyes, ears, and nasal passages.
- Attachment for Muscles: The skull serves as an attachment point for various muscles that control facial expressions, chewing, and head movements. Muscles attached to the skull help in performing essential functions such as eating, speaking, and making facial expressions.
- Sensory Functions: The skull contains structures such as the eye sockets, nasal cavities, and ear canals that house sensory organs responsible for vision, smell, and hearing. These sensory organs are protected within the skull, ensuring their proper functioning.
- Development and Growth: The skull plays a crucial role in the development and growth of the brain and facial structures during infancy and childhood. It provides a protective environment for the developing brain and allows for the expansion of the skull as the brain grows.
In conclusion, the skull's primary function in the human body is to protect the brain and provide structural support for the head and face. Its sturdy and protective nature ensures the safety and well-being of the brain, which is a vital organ responsible for controlling various bodily functions.

Understanding Rib Attachment
In the human body, ribs play a vital role in protecting vital organs and facilitating breathing. The sternum, commonly known as the breastbone, serves as the central anchor point for the ribs.
Types of Ribs
- The ribs are categorized into three main types based on their attachment to the sternum:
- True Ribs: These are the first seven pairs of ribs that have a direct attachment to the sternum.
- False Ribs: The eighth, ninth, and tenth pairs of ribs are considered false ribs because they do not attach directly to the sternum but rather connect to the seventh rib.
- Floating Ribs: The eleventh and twelfth pairs are called floating ribs as they do not attach to the sternum at all.
True Ribs and Their Importance
- Direct Attachment: The seven pairs of true ribs (totaling 14 ribs) are directly connected to the sternum via costal cartilage, providing stability and protection to the heart and lungs.
- Breathing Mechanism: The attachment allows flexibility during breathing, enabling the ribs to expand and contract as the lungs inflate and deflate.
Conclusion
In summary, there are 7 pairs of ribs that are directly attached to the sternum in the human body, making option B the correct answer. Understanding this anatomical detail is crucial for recognizing the body's structure and function, especially in the context of the respiratory system.

The purpose of the backbone is to protect the spinal cord. The backbone, also known as the spine or vertebral column, is a series of bones that extends from the skull to the pelvis. It is made up of individual bones called vertebrae.

**Function of the Spinal Cord:**
The spinal cord is a vital part of the central nervous system. It is responsible for transmitting signals between the brain and the rest of the body. The spinal cord carries sensory information from the body to the brain and relays motor commands from the brain to the muscles and organs. It plays a crucial role in controlling movement, sensation, and bodily functions.

**Protection of the Spinal Cord:**
The spinal cord is a delicate structure that needs protection from injury. The backbone serves as a protective encasing for the spinal cord, shielding it from external forces and impact. The vertebrae, with their strong and sturdy structure, act as a barrier, preventing damage to the spinal cord.

**Flexibility and Support:**
In addition to protecting the spinal cord, the backbone also provides shape and support to the body. The vertebrae are connected by joints that allow for flexibility and movement. This flexibility enables us to bend, twist, and move our bodies in various ways. At the same time, the backbone provides stability and support, maintaining the upright posture of the body.

**Other Functions:**
While the primary purpose of the backbone is to protect the spinal cord, it also serves other functions. The backbone houses and protects the nerves that branch out from the spinal cord, enabling communication between the brain and the rest of the body. Additionally, it provides attachment points for muscles and ligaments, allowing for movement and stability.

In conclusion, the backbone's main purpose is to protect the delicate spinal cord, which is responsible for transmitting signals between the brain and the body. It also provides shape, support, flexibility, and attachment points for muscles and ligaments.

Calcium is essential for keeping our bones strong and healthy. It helps build bone tissue and maintain bone density, reducing the risk of fractures and bone diseases as we grow older.

Cardiac muscle is found in the heart. This type of muscle is involuntary, meaning it works automatically without us having to think about it. It helps pump blood throughout our body.

The function of smooth muscles is to control the movement in our alimentary canal.

Smooth muscles are a type of involuntary muscle tissue found in the walls of various organs and structures in the human body. Unlike skeletal muscles that we can control consciously, smooth muscles work automatically without us having to think about it.

Here are some key points to explain the function of smooth muscles:

1. Controlling movement in the alimentary canal:
- The alimentary canal, also known as the digestive tract, includes organs like the esophagus, stomach, small intestine, and large intestine.
- Smooth muscles in the walls of these organs help in the movement of food through the digestive system.
- They contract and relax in a coordinated manner to push food along the digestive tract, allowing for the digestion and absorption of nutrients.
- This movement is known as peristalsis, which helps in breaking down food and propelling it forward.

2. Involuntary control:
- Smooth muscles are involuntary, meaning they are not under conscious control.
- The contraction and relaxation of smooth muscles are regulated by the autonomic nervous system.
- This allows for the automatic and continuous movement of food through the digestive system, even when we are not actively thinking about it.

3. Other functions of smooth muscles:
- Smooth muscles are also found in other organs and structures in the body, such as blood vessels, bladder, uterus, and respiratory airways.
- In blood vessels, smooth muscles help regulate blood pressure by contracting or relaxing to control the diameter of the vessels.
- In the bladder, smooth muscles contract to expel urine during urination.
- In the uterus, smooth muscles contract during childbirth.
- In the respiratory airways, smooth muscles help regulate airflow by dilating or constricting the bronchial tubes.

Overall, the function of smooth muscles is crucial for the proper functioning of the alimentary canal and other organs in the body. They allow for the involuntary movement of food, fluids, and other substances, ensuring the efficient functioning of our internal systems.

Understanding the Axial Skeleton
The skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton. Understanding these two components helps in identifying the bones that belong to each category.
What is the Axial Skeleton?
The axial skeleton consists of bones that form the central axis of the body. It includes:
- Skull: Protects the brain and forms the structure of the face.
- Vertebrae: Comprises the spinal column, providing support and protecting the spinal cord.
- Sternum: Also known as the breastbone, it connects the ribs and helps in forming the rib cage.
What is the Appendicular Skeleton?
In contrast, the appendicular skeleton includes the bones of the limbs and their attachments to the axial skeleton. This includes:
- Upper limbs: Arms, wrists, and hands.
- Lower limbs: Legs, ankles, and feet.
Why is the Femur Not Part of the Axial Skeleton?
The femur, commonly known as the thigh bone, is classified under the appendicular skeleton because:
- Location: It is located in the leg, which is part of the limbs.
- Function: It plays a crucial role in movement, allowing for walking, running, and other activities involving the legs.
Conclusion
In summary, the femur is not part of the axial skeleton but rather belongs to the appendicular skeleton. The axial skeleton is primarily concerned with protection and support of the body’s central structures, while the appendicular skeleton facilitates movement.

How many pairs of ribs do we have?

The correct answer is option 'C', which is 12.

Explanation:

1. Introduction:
- Ribs are long curved bones that form the ribcage, which protects the vital organs in the chest.
- They are an essential part of the skeletal system and play a crucial role in protecting the heart, lungs, and other organs.

2. Anatomy of Ribs:
- Ribs are thin, flat bones that are connected to the spine at the back and curve around to attach to the sternum (breastbone) at the front.
- There are 12 pairs of ribs in the human body, making a total of 24 ribs.
- Each rib is attached to the vertebrae of the spine by a joint called the costovertebral joint.
- The first seven pairs of ribs are called true ribs because they are directly connected to the sternum by costal cartilage.
- The next three pairs of ribs are called false ribs because they are indirectly connected to the sternum by joining the costal cartilage of the rib above.
- The last two pairs of ribs, known as floating ribs, do not attach to the sternum at all.

3. Function of Ribs:
- Ribs serve several important functions in the body:
- They protect the heart, lungs, and other organs in the chest cavity from injury.
- They provide support and structure to the chest, helping to maintain the shape of the thoracic cavity.
- They play a role in the mechanics of breathing, as they move during inhalation and exhalation to allow for expansion and contraction of the chest cavity.

4. Conclusion:
- In summary, the human body has 12 pairs of ribs, totaling 24 ribs.
- These ribs are essential for protecting vital organs, providing support, and facilitating breathing.
- Understanding the anatomy and function of ribs is important in the study of human biology and healthcare.

The tissue that keeps the bones from rubbing against each other is called cartilage.

Explanation:
Cartilage is a type of connective tissue that is found at the ends of bones where they come together to form joints. It acts as a cushion between the bones, reducing friction and preventing them from rubbing against each other.

Other tissues that are associated with bones include:

• Ligaments - These are tough, fibrous bands that connect bones to other bones, providing stability to joints.

• Tendons - These are cords of tissue that attach muscles to bones, allowing movement.

• Muscle - This tissue is responsible for movement of the body and is attached to bones via tendons.

However, only cartilage serves the function of preventing bones from rubbing against each other.