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Locomotion and Movement - Skeletal system and its functions

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The human skeletal system consists of 206206 bones and a few cartilages, providing a structural framework for the body and facilitating movement.

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The Axial Skeleton (8080 bones) includes the Skull, Vertebral Column, Sternum, and Ribs. The skull is composed of 88 cranial bones and 1414 facial bones.

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The Vertebral Column is formed by 2626 serially arranged units called vertebrae. It protects the spinal cord and supports the head. The regions are Cervical, Thoracic, Lumbar, Sacral, and Coccygeal.

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The Ribs consist of 1212 pairs: True ribs (1st1^{st} to 7th7^{th} pairs), Vertebrochondral/False ribs (8th8^{th}, 9th9^{th}, and 10th10^{th} pairs), and Floating ribs (11th11^{th} and 12th12^{th} pairs).

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The Appendicular Skeleton (126126 bones) comprises the bones of the limbs (Arms and Legs) and the Girdles (Pectoral and Pelvic). Each limb contains 3030 bones.

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Joints are essential for all types of movements involving bony parts. They are classified as Fibrous (immovable), Cartilaginous (limited movement), and Synovial (freely movable).

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Synovial joints are characterized by a synovial cavity filled with fluid, including Ball and Socket, Hinge, Pivot, Gliding, and Saddle joints.

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Bone matrix is hard due to calcium salts like Ca3(PO4)2Ca_{3}(PO_{4})_{2} and CaCO3CaCO_{3}, providing the strength required for weight-bearing.

📐Formulae

Human Vertebral Formula: C7T12L5S(5)Co(4)\text{Human Vertebral Formula: } C_{7} T_{12} L_{5} S_{(5)} Co_{(4)}

Total Bones=Axial Skeleton (80)+Appendicular Skeleton (126)=206\text{Total Bones} = \text{Axial Skeleton (80)} + \text{Appendicular Skeleton (126)} = 206

Bones in one limb=30  ⟹  Total limb bones=30×4=120\text{Bones in one limb} = 30 \implies \text{Total limb bones} = 30 \times 4 = 120

Skull Bones=Cranial (8)+Facial (14)+Hyoid (1)+Ear Ossicles (6)=29\text{Skull Bones} = \text{Cranial (8)} + \text{Facial (14)} + \text{Hyoid (1)} + \text{Ear Ossicles (6)} = 29

💡Examples

Problem 1:

Calculate the total number of bones present in the human hindlimb and name them.

Solution:

The total number of bones in one hindlimb is 3030. These include: 11 Femur (thigh bone), 11 Patella (knee cap), 11 Tibia, 11 Fibula, 77 Tarsals (ankle bones), 55 Metatarsals, and 1414 Phalanges (digits).

Explanation:

According to the appendicular skeletal structure, each limb is designed with 3030 specific bones to facilitate locomotion and weight distribution. The formula for phalanges is 2,3,3,3,32, 3, 3, 3, 3 per foot.

Problem 2:

Differentiate between 'True ribs' and 'Floating ribs' based on their attachment.

Solution:

True ribs (1−71-7 pairs) are attached dorsally to the thoracic vertebrae and ventrally to the sternum via hyaline cartilage. Floating ribs (11−1211-12 pairs) are attached dorsally to vertebrae but are not connected ventrally to the sternum.

Explanation:

True ribs form a complete cage for thoracic protection, whereas floating ribs protect the kidneys and allow for expansion of the lower thoracic cavity.

Problem 3:

A patient has difficulty rotating their head. Which specific joint and vertebrae are likely involved?

Solution:

The Pivot joint between the Atlas (C1C_1) and the Axis (C2C_2) vertebrae is likely involved.

Explanation:

The Atlas is the first cervical vertebra that articulates with the occipital condyles, and the Pivot joint between C1C_1 and C2C_2 allows for the 'no' (rotational) movement of the head.

Skeletal system and its functions - Revision Notes & Key Diagrams | CBSE Class 11 Biology