Animal Tissue
Can you recall? Page No. 116
1. What is tissue?
Answer: A tissue is a group of cells with similar embryonic origin, structure, and function that combine to form organs.
2. Where is squamous epithelial tissue located?
Answer: Squamous epithelial tissue is located in blood vessels, alveoli, and coelom.
3. Enlist functions of bone.
Answer: Bones provide support, protection, and facilitate movement in the skeletal system.
Use your brain power Page No. 118
When do the transitional cells change their shape ?
Answer: Transitional cells change their shape depending on the degree of stretch in the organ, such as when the urinary bladder expands or contracts.
Can you tell? Page No. 119
1. Explain basic structure of epithelial tissue and mention its types.
Answer: Epithelial tissue forms a covering on the inner and outer surfaces of the body and organs, characterized by compactly arranged cells with minimal intercellular matrix, resting on a non-cellular basement membrane. The cells are polygonal, cuboidal, or columnar in shape, with a single nucleus located centrally or at the base, and the tissue is avascular but has good regeneration capacity. It is classified into two main types: Simple epithelium (single layer of cells, e.g., squamous, cuboidal, columnar, ciliated, glandular, sensory, germinal) and Compound epithelium (two or more layers, e.g., stratified, transitional).
2. Epithelial tissue has good capacity of regenereation. Give reason.
Answer: Epithelial tissue has a good capacity for regeneration because its cells have a high rate of cell division and turnover, allowing rapid replacement of damaged or lost cells. The presence of a basement membrane supports cell adhesion and provides a scaffold for new cell growth. This regenerative ability is crucial for maintaining the protective and functional roles of epithelial tissue, such as in skin or intestinal linings.
3. Write a note on glandular epithelial tissue.
Answer: Glandular epithelial tissue consists of columnar, cuboidal, or pyramidal cells with large basal nuclei and secretory granules, specialized for secretion. It forms unicellular glands (e.g., goblet cells in the intestine) or multicellular glands (e.g., salivary glands), classified as exocrine (with ducts, secreting mucus or enzymes, e.g., salivary, sweat glands) or endocrine (ductless, releasing hormones into the bloodstream, e.g., thyroid, pituitary). Its functions include secreting mucus to trap dust or lubricate surfaces, and producing enzymes and hormones to regulate bodily processes.
4. How do cell junctions help in functioning of epithelial tissue?
Answer: Cell junctions are junctional complexes that connect epithelial cells laterally and to the basement membrane, enhancing tissue integrity and function. Tight junctions maintain cell polarity and prevent lateral diffusion, gap junctions facilitate ion and molecule exchange, hemidesmosomes anchor cells to the basement membrane, desmosomes provide mechanical strength, and adherens junctions support signaling pathways. These junctions ensure structural stability, communication, and coordinated functions like protection and secretion in epithelial tissue.
Can you tell? Page No. 122
1. Give reason.
a. Bone is stronger than cartilage.
Answer: Reason: Bone is stronger than cartilage because its matrix, composed of ossein and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂), is harder and more mineralized, providing greater rigidity and tensile strength. Cartilage, with a softer chondrin matrix, is pliable and less mineralized, making it less resistant to mechanical stress. This structural difference allows bones to support and protect the body more effectively than cartilage.
b. As we grow old, cartilage becomes rigid.
Answer: Reason: As we age, cartilage becomes rigid due to the deposition of mineral salts, such as calcium, in its matrix, forming calcified cartilage. This calcification reduces the flexibility of the cartilage, particularly in joints like the head of long bones. The process diminishes the cartilage’s ability to act as a flexible cushion, leading to stiffer joints.
2. Explain histological structure of mammalian bone.
Answer: The histological structure of mammalian bone consists of a hard matrix called ossein, reinforced with hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂), enclosed by a tough outer membrane, the periosteum, through which blood vessels and nerves pass. The matrix is organized into concentric layers called lamellae, containing fluid-filled cavities (lacunae) housing osteoblasts (active bone cells), osteocytes (inactive bone cells), and osteoclasts, connected by fine canals called canaliculi. In compact bones, the haversian system is present, featuring central canals with arteries, veins, and nerves, while spongy bones lack this system, with a reticular matrix of trabeculae containing red bone marrow.
Can you recall? Page No. 122
1. How many skeletal muscles are present in the human body?
Answer: The document does not provide a specific number of skeletal muscles in the human body.
2. How can exercise improve your muscular system?
Answer: The document does not directly detail how exercise improves the muscular system.
Can you tell? Page No. 125
1. Differentiate between medullated and non medullated fibre.
Answer:
| Feature | Medullated (Myelinated) Fibre | Non-Medullated (Non-Myelinated) Fibre |
|---|---|---|
| Myelin Sheath | Present, a fatty insulating layer secreted by Schwann cells. | Absent, no fatty layer. |
| Appearance | White due to myelin sheath. | Grey due to absence of myelin. |
| Conduction Speed | Faster due to saltatory conduction (impulse jumps between Nodes of Ranvier). | Slower, continuous conduction along the axon. |
| Nodes of Ranvier | Present, interruptions in myelin sheath. | Absent, no interruptions. |
| Examples | Cranial nerves of vertebrates. | Nerves of the autonomous nervous system. |
| Function | Prevents impulse loss, efficient for long-distance conduction. | Less efficient, suited for shorter, local conduction. |
2. Classify neuron on the basis of number of processes given out from cyton with examples.
Answer: Neurons are classified based on the number of processes extending from the cyton into three types:
- Unipolar (Monopolar) Neuron: Has a single process originating from the cyton, with both axon and dendron arising from one point. It conducts impulses to the central nervous system.
- Example: Neurons of the dorsal root ganglion of spinal nerve.
- Bipolar Neuron: Has two processes, a single dendron and an axon, extending from opposite poles of the cyton. It transmits special senses like sight, smell, and hearing.
- Example: Neurons of the retina of the eye, olfactory epithelium.
- Multipolar Neuron: Has a star-shaped cyton with more than two processes, including one axon and multiple dendrons, with the axon arising from an axon-hillock. It conducts complex impulses.
- Example: Neurons in the brain and spinal cord.
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