Skeleton

1. Our skeleton consists of bones, cartilages and ligaments
2. Bone is the chief component of our skeleton.
3. Shapewise the bones can be classified as long, short, flat and irregular .
4. The central hollow part of the long bones is known as bone marrow .
5. A bone becomes soft and flexible when placed in dilute hydrochloric acid .

1. False
   Corrected statement — Femur in the thigh is the longest and strongest bone in the body.
2. False
   Corrected statement — Axial skeleton includes skull, vertebral column, ribs and sternum.
3. False
   Corrected statement — There are 7 vertebrae in the neck.
4. True
5. False
   Corrected statement — The shoulder girdle is flat and triangular.

1. True
2. False
   Corrected statement — The muscles can contract but cannot elongate.
3. False
   Corrected statement — Muscles are attached to bones by tendons.
4. False
   Corrected statement — Cardiac muscle is an involuntary muscle.
5. True

Cartilage

Reason — External ear is made up of cartilage due to which it is flexible.
The pinna is not made of bone. Bone is found in the middle ear (auditory ossicles), not in the external ear. Tendons connect muscle to bone. They do not form or support the ear structure. Capsules are protective coverings of organs or joints, not structural support for the ear.

Hip

Reason — Shoulder has ball and socket joint,which allows movement in multiple directions and is also found in Hip.
The elbow is a hinge joint, allowing movement in one plane (like bending and straightening). The knee is also a hinge joint, mainly for bending and straightening. The ankle is a hinge joint that mainly allows up and down movement of the foot.

Cervical — 7

Reason — There are seven cervical vertebrae, twelve thoracic, five lumbar and five sacral.
Thoracic vertebrae are 12, not 10. They are attached to ribs (T1–T12). Lumbar vertebrae are 5, not 4. They form the lower back (L1–L5). The sacral vertebrae are 5 fused vertebrae, not 4, forming the sacrum.

Ear ossicles

Reason — Ear ossicles have 3 bones in each ear (malleus, incus and stapes); making a total of 6 bones.
The neck has 7 cervical vertebrae. Carpals are 16 in total (8 in each hand). Metacarpals are 10 in total (5 in each hand).

Ligaments

Reason — Ligaments hold bones together.
Tendons connect muscles to bones, not bones to each other. Cartilage is a flexible connective tissue that cushions bones at joints but does not primarily bind bones together. Muscles help in movement by contracting and relaxing, but they do not bind bones.

Calcium and phosphorus

Reason — Calcium and phosphorus are major components of bone.Bones contain inorganic salts mainly as calcium phosphate, which provides hardness and strength.
Sodium is present in body fluids, but it is not a major inorganic component of bones. Carbon and nitrogen are organic elements found in proteins (like collagen), not the main inorganic bone minerals. Carbon is part of organic compounds, not the primary inorganic bone material.

Osteocytes

Reason — Osteocytes is the technical term used for bone cells.
Myocytes are muscle cells, not bone cells. Chondrocytes are cartilage cells, found in cartilage tissue. Leucocytes are white blood cells involved in immunity.

Periosteum

Reason — Periosteum is a complex structure composed of an outer fibrous layer that lends structural integrity and an inner cambium layer that possesses osteogenic potential.
The peritoneum is a membrane lining the abdominal cavity, not related to bones. The pericardium is the membrane surrounding the heart.

Iris

Reason — Iris is made up of involuntary muscles.
Leg muscles are skeletal (voluntary) muscles, controlled consciously. Hand muscles are also skeletal (voluntary) muscles. Most muscles in the head (like facial muscles) are voluntary skeletal muscles, not involuntary.

S and p

Reason — Cardiac muscles are involuntary and found only in the heart. They are striated and branched and contract rhythmically throughout life.

P — Pelvic, Q — Pelvic

Reason — Both ischium and pubis are part of the pelvic girdle, not different girdles. The pelvic girdle is made up of three bones: Ilium, Ischium and Pubis.
Pectoral girdle is the shoulder region. Ischium and pubis are not part of pectoral girdle. Ischium and pubis are hip bones. Pubis is not part of pectoral girdle.

R and S

Reason — R- Calcium strengthens bones. Proteins help in bone repair and maintenance.
S- Vitamin D helps the body absorb calcium efficiently, essential for bone health.
P- Excess salt can actually increase calcium loss from bones. Sugar-rich foods do not help bone health. Q- Food items rich in carbohydrates and fats.

Two parts of your body where the supporting skeleton is made of cartilage instead of bone are:

1. External Ear
2. Tip of the nose

(a) Bones, Cartilages and Ligaments

(b) Axial skeleton and Appendicular skeleton

(c) Skull, Vertebral Column, Sternum, Ribs

(d) Cervical, Thoracic, Lumbar, Sacrum, Coccyx

(e) Gliding joint, Pivot joint, Hinge joint, Ball and Socket joint.

The upper arm consists of a single long bone, called Humerus . Two long bones are found in the lower arm, Radius found on the side of the thumb and Ulna . Forelimbs have eight Carpals in the wrist and five Metacarpals in the palm. Remaining fourteen bones are found in the fingers as phalanges.

(a) Ball and socket joint

(b) Atlas

(c) Foramen Magnum

(d) Antagonistic Muscles

(e) Synovial fluid

(a) Humerus : Glenoid cavity :: Femur : Articular Cavity

(b) Thoracic vertebrae : 12 : Cervical : 7

(c) Wrist : Carpals :: Ankle : Tarsal

(d) Biceps : Flexor :: Triceps : Extensor

(e) Brain : Cranium :: Spinal cord : Vertebral column

(a) Knee cap — Patella

(b) Shoulder blade — Scapula

(c) Collar bone — Clavicle

(d) Breast bone — Sternum

(e) Bones in the palm — Metacarpals

(a) Skeleton System refers to the internal framework of bones and other connective tissues including cartilage, ligaments, and tendons that provide support, shape, protection, movement and leverage to the human body.

(b) Bone marrow is a soft, spongy tissue found inside the central hollow space or the marrow of some of the long bones where certain types of blood cells including red and white blood cells are formed.

(c) A pad of cartilage intervertebral disc that forms a kind of cushion between two vertebrae is called Gristle.

(d) Joint that allow rotation about an axis is called Pivot joint.

(e) The muscles that cause opposing movements are called antagonistic muscles.

The muscles in the body provide the means of all movements. Muscles pull the structures. Each muscle usually has two ends- a fixed end where the muscle originates and a movable end which pulls some other part. The movable end is shorter and thicker and hence pulls the bone at the movable end. Muscles can only contract and relax, they cannot lengthen or elongate.
The movable end is projected out to form a tough structure referred to as a tendon which is attached to the bone. When a muscle is triggered by a nerve, contraction of the muscle occurs and it becomes thicker and shorter which causes the bone to be pulled at the movable end.

A structure that has been moved by a muscle cannot return to its original position without the action of another muscle. Such muscles causing opposing movements are called as antagonistic muscles.

Example of antagonistic muscles—
The flexor muscles or the biceps of the upper arm bends the lower arm over the upper arm (flexes). Extension of the lower arm is caused by the extensor muscles or the triceps. Hence these two muscles are antagonistic or work in the opposite direction.

(a) Two-third of entire bone mass is made of calcium and phosphorous. It gives strength and hardness to bones. Therefore, when these inorganic substance are lost or the bone is decalcified, they become soft and flexible.

(b) The freely movable joints are well lubricated by synovial fluid to remove friction between the joint surfaces. With age, the production and quality of synovial fluid decreases, leading to less effective lubrication. This coupled with degeneration of cartilage and ligaments causes stiff joints in old age.

(c) In the female skeleton, the pelvis or hip bone is wider and trough-shaped to adapt for accommodating the foetus in the uterus during pregnancy.

(d) Bones are made up of living cells (osteocytes) that are responsible for their growth, maintenance, and repair. They receive blood supply through a network of blood vessels and they produce red and white blood cells within the bone marrow. Therefore, the bones are considered to be a living tissue.

(e) Vertebral column is curved in order to provide correct posture and balance to our body. It's curvature enables us to minimize all the stress on bones and muscles that arises due to activities.

(a) Thigh

(b) Ear

(c) lower part of back bone

(d) Brain box

(e) In the middle of the front part of the chest.

(a) Difference between true ribs and floating ribs:

(b) Difference between ligaments and tendons:

(c) Difference between hinge joint and gliding joint:

(d) Difference between voluntary and involuntary muscles :

(e) Difference between Bone and cartilage :

Uses of skeleton:

1. Support and shape — The skeletal system provides a framework to the body. It provides support to all soft parts and gives a definite shape to the body and all body parts.
2. Protection — Several delicate and important organs are well protected by a casing of bones.
   Example — The skull provides protection to the delicate brain.
3. Movement — Some bones are movable on each other which is brought about by the action of muscles that originate on one bone and are inserted into another.
4. Leverage — Some bones and joints form levers which causes the increase in the speed and distance of the muscle movement.
5. Formation of blood cells — Certain types of blood cells including red and white blood cells are formed in the marrow of certain long bones such as the femur.
6. The bones are storehouse of calcium and phosphorus for the rest of the body.

Types of joints with examples are:

1. Immovable joints — Skull bones
2. Partially movable joints — Joints between the ribs and breast-bone
3. Freely movable joints — Hip joint
4. Gliding joint — Ankle bones
5. Pivot joint — Joint between axis vertebrae and atlas
6. Hinge joint — Elbow
7. Ball and socket joint — Shoulder joint

(a) Thoracic vertebra.

(b) Thoracic region of vertebral column.

(c) The labelled guidelines are:

• 1 → Neural spine
• 2 → Neural canal
• 3 → Body of centrum

(a) Synovial Joint

(b) The shoulder joint and the knee joint.

(c) Ligament

• 1 → Skull/Cranium
• 2 → Clavicle
• 3 → Sternum
• 4 → Humerus
• 5 → Ulna
• 6 → Coccyx
• 7 → Ribs
• 8 → Radius
• 9 → Femur
• 10 → Fibula
• 11 → Tibia

A is False and R is True.

Reason — A is False as the axial skeleton consists of the central core of the body: Skull, vertebral column, rib cage and sternum. It does not include the limbs or girdles.
R is True as the axial skeleton forms the central supporting axis of the body.

Therefore, A is False and R is True is the correct option.

A is True and R is False.

Reason — A is True as each hip bone is formed by the fusion of three bones: Ilium, Ischium and Pubis. These fuse during development to form a single structure.
R is False as the hip bone is a part of the pelvis, not the same as the pelvis. The pelvis includes: Two hip bones, sacrum and coccyx. The female pelvis is wider, shallower, and more rounded, to facilitate childbirth.

Therefore, A is True and R is False is the correct option.

A is True and R is False.

Reason — A is True as synovial fluid is a viscous fluid present in synovial joints. It reduces friction, lubricates the joint, and nourishes the articular cartilage.
R is False as the bones of the cranium are connected by immovable joints called sutures, not synovial joints. Sutures are fibrous joints that do not contain synovial fluid.

Therefore, A is True and R is False is the correct option.

Both A and R are true but R is not the correct explanation of A.

Reason — A is true as a hinge joint allows movement in one plane (like a door hinge) and is found in the elbow, knee, ankle, and fingers.
R is true as the elbow is a hinge joint, which allows movement in only one direction (flexion and extension, like a door hinge).
Their main characteristic of hinge joint is restricted one-direction movement, not power.

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

Both A and R are true and R is the correct explanation of A.

Reason — A is true as the radius and ulna are the two long bones of the forearm. They extend from the elbow to the wrist.
R is true as the radius and ulna connect the upper arm bone (humerus) to the wrist bones (carpals), forming the forearm.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

A is False and R is True.

Reason — A is False as the sternum is not formed by vertebrae. It is a flat bone located in the center of the chest (anterior thoracic region).
R is True as it is located in the center of the chest, and connects to the ribs via cartilages, playing a vital role in protecting the heart and lungs.

Therefore, A is False and R is True is the correct option.

(a) The joints belong to the skeletal system.

(b) Two functions other than support and shape are :

1. Protection of internal organs.
2. Movement with the help of muscles.

(c) The kind of joints found at elbow is hinge joint and hip is ball-and-socket joint.

(d) A structure of the human body where bones are joined to each other but no movement is possible is skull (cranium).

(e) Fluid between the two bones of freely movable joints is synovial fluid.