Human Anatomy IV: Main Exam, 11 November 2025

Mount Kenya University · Department of Dental Sciences · Diploma in Dental Technology · DHA2101

Human Anatomy IV past paper from Mount Kenya University 2024-2025 with model answers.

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

SECTION A (30 marks)

1. Explain the general principles of embryology (8 marks)

Model answer
  • Cell lineage: Embryology studies the origin and differentiation of cells from the fertilized ovum to adult tissues.
  • Germ layers: Three primary germ layers (ectoderm, mesoderm, endoderm) form during gastrulation and give rise to all organs.
  • Organogenesis: Sequential formation of organs from germ layers through morphogenetic movements and signaling pathways.
  • Timing: Development is divided into pre‑embryonic (0‑2 weeks), embryonic (3‑8 weeks) and fetal periods (9 weeks‑birth).
  • Regulation: Gene expression, growth factors and epigenetic mechanisms control cell fate and patterning.
  • Plasticity: Early embryonic cells are totipotent, then become pluripotent and later multipotent.
  • Apoptosis: Programmed cell death removes unnecessary cells, shaping structures.
  • Environmental influence: Nutrition, teratogens and maternal health can alter normal development.

2. Differentiate between mitosis and meiosis in cell division (8 marks)

Model answer
  • Purpose: Mitosis produces two genetically identical diploid cells for growth and repair; meiosis generates four genetically diverse haploid gametes for reproduction.
  • Number of divisions: Mitosis involves one division (prophase‑metaphase‑anaphase‑telophase); meiosis has two successive divisions (Meiosis I and Meiosis II).
  • Chromosome number: Daughter cells retain the parental chromosome number (2n) in mitosis; gametes are halved (n) after meiosis.
  • Crossing‑over: Absent in mitosis; occurs during prophase I of meiosis, increasing genetic variation.
  • Synapsis: Homologous chromosomes pair only in meiosis I; no pairing in mitosis.
  • Resulting cells: Mitosis yields two cells; meiosis yields four cells.
  • Genetic identity: Mitosis produces clones; meiosis produces genetically unique cells.
  • Role in life cycle: Mitosis maintains somatic cell populations; meiosis is essential for sexual reproduction.

3. Identify key steps in fertilization (7 marks)

Model answer
  • Capacitation: Sperm undergo biochemical changes in the female tract to become fertilization‑competent.
  • Acrosome reaction: Enzyme release allows sperm to penetrate the zona pellucida of the oocyte.
  • Sperm‑egg binding: Specific receptors on the zona pellucida (ZP3) bind to sperm surface proteins.
  • Cortical reaction: Fusion of sperm and oocyte membranes triggers calcium influx, causing cortical granule exocytosis that prevents polyspermy.
  • Pronuclear formation: Male and female pronuclei form and migrate toward each other.
  • Syngamy: Fusion of pronuclei restores diploid chromosome complement.
  • Activation of embryonic development: Initiation of the first mitotic division (cleavage).

4. Outline the development of epidermis in the human body (7 marks)

Model answer
  • Ectodermal origin: Epidermis derives from the surface ectoderm during the third week of embryogenesis.
  • Surface ectoderm thickening: Forms the epidermal placode which proliferates to create a multilayered epithelium.
  • Stratification: Basal keratinocytes divide and migrate outward, forming basal, spinous, granular and cornified layers.
  • Keratinisation: Production of keratin and formation of the stratum corneum provides barrier function.
  • Melanocyte migration: Neural‑crest melanocytes migrate into the basal layer, giving skin colour.
  • Hair follicle & gland development: Interaction with underlying mesenchyme induces formation of hair follicles, sebaceous and sweat glands.
  • Barrier maturation: Lipid secretion and desquamation complete the functional epidermis.

SECTION B (40 marks)

1. Explain the development process of connective tissues in the human body

Model answer
  • Mesenchyme origin: Connective tissue begins as loosely organized mesenchymal cells derived from the mesoderm (and neural crest for craniofacial regions).
  • Cell proliferation: Mesenchymal cells proliferate and migrate to future tissue sites.
  • Differentiation cues: Growth factors (FGF, TGF‑β) and extracellular matrix signals direct cells toward specific lineages (fibroblasts, chondrocytes, osteoblasts, adipocytes).
  • Extracellular matrix deposition: Cells synthesize collagen, elastin, proteoglycans and glycosaminoglycans, forming the connective tissue matrix.
  • Maturation: Matrix cross‑linking (lysyl oxidase) and fiber alignment increase tensile strength.
  • Vascularisation: Angiogenic factors promote blood vessel ingrowth to supply nutrients.
  • Remodelling: Matrix metalloproteinases remodel the matrix during growth and wound healing.
  • Specialisation: Regional signals produce specialised connective tissues such as tendons, ligaments, cartilage and bone.

2. Write notes on the stages of development of cartilage

Model answer
  • Mesenchymal condensation: Mesenchymal cells aggregate and differentiate into chondroblasts.
  • Chondroblast proliferation: Cells secrete cartilage matrix (type II collagen, proteoglycans) forming a cartilage model.
  • Hypertrophy: Central chondrocytes enlarge, produce type X collagen and begin mineralisation.
  • Calcification & vascular invasion: Matrix calcifies, blood vessels invade, bringing osteoprogenitor cells.
  • Primary ossification centre formation: Osteoblasts replace cartilage with bone tissue.
  • Secondary ossification centres: Appear in epiphyses, completing growth plate development.
  • Growth plate activity: Continual chondrocyte division at the epiphyseal plate lengthens the bone until adulthood.

3. Discuss the functions of amniotic fluid in embryonic development

Model answer
  • Protection: cushions the embryo against mechanical trauma and prevents compression.
  • Growth medium: provides a buoyant environment allowing free movement, which promotes musculoskeletal development.
  • Physiological functions: maintains constant temperature, supplies nutrients, facilitates waste removal, and prevents adhesion of fetal membranes.
  • More answers:
  • Supports lung development by allowing fetal breathing movements.
  • Acts as a medium for antimicrobial factors that protect against infection.
  • Helps regulate fetal fluid balance and electrolyte composition.

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