OBJECTIVE QUESTIONS

1. The skin is covered with a layer of dead cells forming resistant covering known as:
   (c) Stratum corneum
2. Antlers are found in:
   (a) Deer
3. What type of skeleton is present outside the body of the animal:
   (b) Dermal skeleton
4. The vertebrate group lacking true teeth:
   (a) Fishes
5. The chief respiratory organs in aquatic vertebrates are:
   (c) Gills

SUBJECTIVE QUESTIONS

Answer any two of following

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(i) Explain the Structure and Functions of Integuments

The integument refers to the outer covering of the body, primarily the skin and its associated structures. It plays a crucial role in protection, sensation, and regulating body functions. The integument is typically divided into two main layers:

Structure:

1. Epidermis (outer layer):

• Made of stratified squamous epithelium.
• Contains keratinocytes (which produce keratin), melanocytes (responsible for skin pigmentation), and Langerhans cells (involved in immune response).
• The stratum corneum is the outermost layer of dead keratinized cells, providing a tough, protective barrier.

1. Dermis (inner layer):

• Composed of connective tissues, containing collagen fibers, blood vessels, nerves, hair follicles, and sweat glands.
• Contains two regions:
  • Papillary layer: Provides nutrients to the epidermis.
  • Reticular layer: Offers strength and elasticity.

1. Hypodermis (subcutaneous tissue):

• Consists mainly of fat and connective tissues for insulation and energy storage.

Functions:

• Protection: Forms a physical barrier against environmental damage, pathogens, and UV rays.
• Sensation: Contains sensory receptors for touch, temperature, pain, and pressure.
• Thermoregulation: Sweat glands and blood vessels help regulate body temperature.
• Excretion: Sweat removes wastes like urea and salts.
• Water resistance: Prevents excessive water loss from the body.

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(ii) Explain Briefly the Types of Bones and Bone Formation

Types of Bones:

1. Long Bones:

• Found in limbs (e.g., femur, humerus).
• Provide support and facilitate movement.

1. Short Bones:

• Found in wrists and ankles (e.g., carpals, tarsals).
• Provide stability and some movement.

1. Flat Bones:

• Found in the skull, ribs, and scapula.
• Protect internal organs and provide surface area for muscle attachment.

1. Irregular Bones:

• Have complex shapes (e.g., vertebrae, pelvic bones).
• Protect organs and support the body.

1. Sesamoid Bones:

• Found within tendons (e.g., the patella).
• Protect tendons from stress and wear.

Bone Formation (Ossification):

• Intramembranous Ossification:
• Occurs in flat bones (like the skull).
• Bone forms directly from mesenchymal tissue (primitive connective tissue).
• Endochondral Ossification:
• Occurs in long bones and most other bones.
• Bone develops from a cartilaginous model, which gradually gets replaced by bone tissue.

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(iii) Write a Short Note on Accessory Organs of the Buccal Cavity

The buccal cavity (mouth) plays an essential role in digestion, and its accessory organs assist in the process. These organs are:

1. Teeth:

• Responsible for mechanical digestion by chewing and grinding food.
• There are different types: incisors, canines, premolars, and molars.

1. Tongue:

• A muscular organ with taste buds.
• Helps in manipulating food, tasting, and swallowing. It also plays a role in speech.

1. Salivary Glands:

• Produce saliva, which contains enzymes like amylase that begin the digestion of carbohydrates.
• Major salivary glands include parotid, submandibular, and sublingual glands.

1. Palate:

• The hard and soft palate separate the buccal cavity from the nasal cavity.
• The soft palate helps in swallowing by closing off the nasal passages.

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(iv) Discuss the Structure of a True Gill

True gills are the respiratory organs found in aquatic animals, such as fish, and are responsible for gas exchange.

Structure of a True Gill:

1. Gill Arch:

• A bony or cartilaginous structure that supports the gill filaments.

1. Gill Filaments:

• Thin, long structures arranged in pairs on each side of the gill arch.
• Each filament has lamellae, which increase the surface area for gas exchange.

1. Lamellae:

• These are thin plates containing a network of capillaries where the exchange of gases (oxygen and carbon dioxide) occurs.

1. Gill Rakers:

• Present on the inner edge of the gill arches.
• Prevent debris and large particles from damaging the gills.

1. Countercurrent Exchange Mechanism:

• Blood flows through the gill capillaries in the opposite direction to the water passing over the gills, maximizing oxygen uptake.

Function:

• Gas Exchange: Oxygen is absorbed from water, and carbon dioxide is released.
• Osmoregulation: Helps maintain ion balance in the body.
• Excretion: Eliminates some nitrogenous wastes like ammonia directly into the water.

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