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Tissues - The Musculoskeletal System

Grade 9CBSE

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

🔑Concepts

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Muscular tissue consists of elongated cells, also called muscle fibers, containing contractile proteins like actin and myosin that facilitate movement through contraction (contractioncontraction) and relaxation (relaxationrelaxation).

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Striated (Skeletal) muscles are voluntary, show alternate light and dark bands (striations), and possess long, cylindrical, unbranched, and multinucleated cells.

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Smooth (Unstriated) muscles are involuntary, spindle-shaped, uninucleated, and lack striations. They are found in the walls of internal organs like the stomachstomach and intestinesintestines.

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Cardiac muscles are involuntary, branched, cylindrical, and uninucleated cells found only in the heart, performing rhythmic contraction and relaxation throughout life.

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Bone is a supportive connective tissue with a hard matrix composed of calcium and phosphorus compounds, specifically hydroxyapatite with the formula Ca10(PO4)6(OH)2Ca_{10}(PO_4)_6(OH)_2.

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Ligaments are highly elastic connective tissues that connect two bones (Bone−to−BoneBone-to-Bone), while Tendons are fibrous tissues with great strength but limited flexibility that connect muscles to bones (Muscle−to−BoneMuscle-to-Bone).

📐Formulae

Ca3(PO4)2 (Calcium Phosphate in bone matrix)Ca_3(PO_4)_2 \text{ (Calcium Phosphate in bone matrix)}

F=m×a (Force exerted by muscular contraction)F = m \times a \text{ (Force exerted by muscular contraction)}

Work Done(W)=F×dcos⁡(θ)\text{Work Done} (W) = F \times d \cos(\theta)

💡Examples

Problem 1:

Calculate the total number of nuclei in a sample containing 1515 smooth muscle cells and 55 striated muscle fibers (assuming each striated fiber has approximately 44 nuclei for this calculation).

Solution:

15×1+5×4=15+20=3515 \times 1 + 5 \times 4 = 15 + 20 = 35

Explanation:

Smooth muscle cells are uninucleated (1 nucleus per cell), whereas striated muscle fibers are multinucleated. In this specific calculation: 15×115 \times 1 for smooth muscles and 5×45 \times 4 for striated fibers gives a total of 3535 nuclei.

Problem 2:

A researcher is analyzing a tissue sample. The matrix is hard and rich in Ca2+Ca^{2+} and PO43−PO_4^{3-} ions. Identify the tissue and the chemical compound formed.

Solution:

The tissue is Bone and the compound is Calcium Phosphate (Ca3(PO4)2Ca_3(PO_4)_2).

Explanation:

The presence of a hard matrix containing Calcium and Phosphorus is a characteristic feature of bone cells (osteocytes) which provide the structural framework for the musculoskeletal system.

Problem 3:

During a laboratory test, the total mass of a bone sample was found to be 12001200 units. After removing organic matter, the mineral content remained at 800800 units. Calculate the organic mass removed using vertical subtraction.

Solution:

1200−800400\begin{array}{r} 1200 \\ - 800 \\ \hline 400 \end{array}

Explanation:

To find the organic mass, subtract the mineral weight from the total bone mass: 1200−800=4001200 - 800 = 400 units.