Human Physiology IV: Main Exam, November 2017

Mount Kenya University · Department of Dental Sciences · Diploma in Community Oral Health · DDS2111

Human Physiology IV past paper from Mount Kenya University 2017-2018 with model answers for dds2111 unit.

Instructions: ANSWER ALL QUESTIONS IN SECTION A AND ANY OTHER TWO IN SECTION B

SECTION A (30 marks)

1. Define the following terms:

  1. a) Thermo regulation
    Model answer
    • Thermoregulation: The physiological processes that maintain core body temperature within a narrow optimal range despite external temperature changes.
  2. b) Fever
    Model answer
    • Fever: A regulated rise in body temperature above the normal set point, usually in response to infection or inflammation.
  3. c) Taste buds
    Model answer
    • Taste buds: Specialized sensory papillae on the tongue containing gustatory receptor cells that detect sweet, salty, sour, bitter and umami stimuli.
  4. d) Hyperpyrexia
    Model answer
    • Hyperpyrexia: An extreme fever, typically a core temperature exceeding 41.5 °C (106.7 °F), requiring urgent medical intervention.
  5. e) Metabolic Rate
    Model answer
    • Metabolic Rate: The amount of energy expended by the body per unit time, usually expressed as basal metabolic rate (BMR) in kcal/day.

2. Draw a well labeled diagram showing taste zone.

Model answer
  • Diagram description: Show a lateral view of the tongue with the circumvallate, foliate, and fungiform papillae highlighted as the main taste zones. Include labels for:
  • Circumvallate papillae (posterior tongue)
  • Foliate papillae (lateral margins)
  • Fungiform papillae (anterior tip and dorsum)
  • Taste bud clusters within each papilla
  • Lingual epithelium surface
  • Glossopharyngeal nerve (IX) and facial nerve (VII) pathways indicated.

3. Classify hypothermia.

Model answer
  • Hypothermia classification
  • Mild: 32–35 °C (98.6–95 °F)
  • Moderate: 28–32 °C (82.4–89.6 °F)
  • Severe: <28 °C (82.4 °F)

4. Briefly explain how shivering takes place in heat production.

Model answer
  • Shivering mechanism
  • Trigger: Hypothalamic thermoregulatory centre senses ↓core temperature
  • Signal: Sympathetic output to skeletal muscle
  • Action: Rapid, involuntary muscle contractions
  • Heat production: Mechanical work converted to metabolic heat
  • Feedback: Rising temperature reduces shivering intensity

5. Explain the function of olfactory cilia of the nose.

Model answer
  • Olfactory cilia function
  • Detection: Bind odorant molecules in mucus
  • Signal transduction: Activate olfactory receptor neurons
  • Transmission: Send impulses via olfactory nerve to brain
  • Perception: Odor identification and discrimination

6. Draw a well labeled diagram showing parts of the skin.

Model answer
  • Diagram description
  • Layers: Epidermis, Dermis, Hypodermis
  • Epidermis: Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale
  • Dermis: Papillary dermis, Reticular dermis
  • Hypodermis: Subcutaneous fat
  • Other structures: Hair follicle, sebaceous gland, sweat gland, blood vessels, nerves

7. Write short notes on apocrine sweat glands.

Model answer
  • Apocrine sweat glands
  • Location: Axillae, anogenital region, areola
  • Secretion: Thick, milky fluid rich in proteins
  • Trigger: Sympathetic cholinergic stimulation
  • Function: Thermoregulation and pheromone release
  • Odor: Bacterial breakdown causes body odor

8. Briefly explain two parts of the ear, indicating their function.

Model answer
  • External auditory canal
  • Function: Conducts sound waves to tympanic membrane
  • Middle ear
  • Function: Amplifies and transmits vibrations via ossicles to inner ear

SECTION B (40 marks)

1. Discuss functions of the skin.

Model answer
  • Barrier protection: Prevents entry of pathogens, chemicals and physical trauma.
  • Regulation of body temperature: Through sweating and vasodilation/vasoconstriction.
  • Sensory reception: Contains mechanoreceptors, thermoreceptors and nociceptors for touch, pressure, temperature and pain.
  • Excretion: Eliminates waste products such as urea and salts via sweat.
  • Vitamin D synthesis: UV‑B radiation converts 7‑dehydrocholesterol to pre‑vitamin D3.
  • Water balance: Controls transepidermal water loss and re‑absorption.
  • Immune function: Langerhans cells detect antigens and initiate immune responses.
  • Aesthetic & communication role: Skin colour, texture and hair convey social and health information.

2. Body temperature regulation occurs in two way; heat production and heat loss, disc

Model answer
  • Heat production: Metabolic activity (basal metabolism, muscle shivering) generates heat.
  • Heat loss:
  • Radiation: Emission of infrared energy from skin surface.
  • Conduction: Direct transfer of heat to cooler objects in contact.
  • Convection: Air or water flow removes heat from skin.
  • Evaporation: Sweat evaporation absorbs latent heat, cooling the body.
  • Vasomotor control: Vasodilation increases heat loss; vasoconstriction reduces it.
  • Behavioral responses: Changing clothing, seeking shade or warmth, adjusting activity level.

3. Explain the skin appendages.

Model answer
  • Hair: Provides insulation, sensory function and protection; consists of a shaft, follicle and associated sebaceous gland.
  • Nails: Protect distal phalanges, aid fine manipulation; composed of hard keratin plates.
  • Sweat glands:
  • Eccrine glands: Widely distributed, produce watery sweat for thermoregulation.
  • Apocrine glands: Located in axillae and groin, secrete viscous fluid that contributes to body odor.
  • Sebaceous glands: Secrete sebum onto the skin surface, lubricating hair and skin and providing antimicrobial lipids.
  • Sensory receptors: Merkel cells, Meissner’s corpuscles, Pacinian corpuscles and free nerve endings embedded in the dermis and epidermis.
  • Arrector pili muscles: Small smooth muscles attached to hair follicles that cause goose‑bumps when contracted.

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