Human Fertilisation and Embryonic Stage Quiz

Human Fertilisation

• Fertilisation is the union of sperm and ovum, creating a zygote which implants in the uterine wall after 8-9 days.
• The blastocyst, at 6 days, consists of the inner cell mass (future fetus), trophoblast (future placenta), and blastocoel (fluid-filled cavity).
• The embryo implants in the endometrium (uterine lining).

Embryonic Stage

• Begins after implantation and lasts until 8 weeks after conception.
• The embryo forms primary germ layers: ectoderm, mesoderm, and endoderm through gastrulation.
• The layers develop into various tissues and organs:
  • Ectoderm: skin, hair, brain, nervous tissue.
  • Mesoderm: connective tissue, circulatory system, muscles, bones.
  • Endoderm: digestive system, lungs, urinary system.
• Significant developments occur each week:
  • Week 3: Brain, heart, spinal cord, and digestive system development begins.
  • Week 4: Facial structures, limb buds, and a beating heart form.
  • Week 5: Eyes, nose, kidneys, lungs, and heart valves develop.
  • Week 6: Hands, feet, and digits form with continued brain and heart development.
  • Week 7: Hair follicles, sex organs, and brain waves develop.
  • Week 8: Distinct facial features, well-developed internal organs, and the brain controls muscle movements.
• By the end of the embryonic stage, all essential structures are formed, and the embryo is called a fetus.

Fetal Stage

• Begins around week 8 after conception and continues until birth.
• At 8 weeks, the fetus measures 3 cm and weighs 3 grams.
• By 38 weeks (full term), the fetus measures 50 cm and weighs 3.3 kg.
• The fetus becomes more active, and the mother may feel movements (quickening).
• Body proportions become more balanced.
• Significant developments occur each trimester:
  • 6th month: The fetus is 28.5 cm and weighs 0.7 kg. Hair grows on the body, eyelids form, and lung air sacs (alveoli) develop.
  • 7th month: The fetus is 38 cm and weighs 1.2 kg. Rapid brain development occurs, and the fetus has more control over movements. The lungs continue developing, and the fetus would be capable of breathing air if born prematurely.
  • 8th month: The fetus grows to 38-43 cm and weighs 2 kg. Fat deposits increase under the skin, and bones develop. The lungs remain immature, but breathing movements begin.
  • 9th month: The fetus measures 41-48 cm and weighs 2.6 -3.0 kg. Lanugo starts to disappear, and fingernails fully grow. The fetus gains control over body function and fat accumulates.
  • Full term (36-38 weeks): The fetus measures 48-53 cm. Lanugo is mostly gone, and fingernails extend past the fingertips. All organ systems are fully functioning, preparing the fetus for birth.

Common Problems During Prenatal Development

• Congenital abnormalities can result from genetic factors, environmental influences, or a combination of both.
• Survival rates vary depending on gestational age:
  • 21 weeks or less: 0 percent survival rate
  • 22 weeks: 0–10 percent survival rate
  • 23 weeks: 10–35 percent survival rate
  • 24 weeks: 40–70 percent survival rate
  • 25 weeks: 50–80 percent survival rate
  • 26 weeks: 80–90 percent survival rate
  • 27 weeks: greater than 90 percent survival rate

Brain Development

• Brain development starts around 18 days after conception with the formation of the neural plate, which forms the neural tube (future brain and spinal cord).
• Neurons form rapidly during prenatal development, creating neuronal circuits and synapses essential for brain function.
• Brain growth is most rapid during the first two years of life, with significant increases in size and complexity due to neuronal growth, glial cell growth, and myelination of axons.
• This growth supports the development of infant and young child motor skills.
• Brain development continues throughout life through synaptic pruning and the formation of new neural connections, influencing learning and adaptation to new experiences.
• The brain is divided into three main parts:
  • Brain stem: connects the spinal cord to the brain and controls reflexes and involuntary functions.
  • Cerebellum: behind the brain stem, helps with balance and coordination.
  • Cerebrum: responsible for higher-level functions like thinking, learning, and memory.

Foundational Behaviors (4-7 Months)

• Infants may have a range of vision, recognize familiar objects, startle at loud noises, and explore textures.

Exploratory Behaviors (9-17 Months)

• Infants may nuzzle into familiar fabrics, recognize sounds associated with daily activities, and engage in messy play.

Sensory Interaction (19-35 Months)

• Children enjoy various tactile experiences: playing with sand and water, handling fragile items, enjoying tactile books.

Motor Skills Development

• Motor skills involve coordinated and controlled movements using muscles.
• Motor behavior encompasses all body movements, including eye movements (gaze) and the infant's developing control of the head.

Gross Motor Skills

• Activities like walking, running, and jumping require the coordination of large muscle groups.
• Gross motor development serves as the foundation for physical activity, contributing to maintaining healthy weights.
• It has been shown to improve academic performance.
• Gross motor skills start developing in infancy and continue throughout childhood.

The Developing Ability to Move Large Muscles

• During the 6-9 months age:
  • Children can sit with bent legs and use forearms to pull themselves while on their stomach.

The Interconnection Between Physical, Cognitive, and Social Development

• Physical development is related to cognitive and social development.
• Motor skills allow children to explore and play with others, which encourages learning and socializing.
• Challenges in communication and interaction due to failure in gross motor development milestones highlight the importance of considering all physical aspects in child assessments.

Continuous Monitoring of Physical Development

• Physical development is a process, and regular assessments are necessary to track growth patterns and motor skill development.
• Early identification and interventions can prevent worsening situations.

Cultural and Environmental Factors in Physical Development

• Socioeconomic status influences a child's access to food, medical care, and sports. These factors need to be considered during assessments to ensure interventions are tailored to individual needs.

Summary

• Physical development encompasses the growth and refinement of motor skills, body functions, and overall health from the prenatal stage through adulthood.
• Prenatal development, including the germinal, embryonic, and fetal stages, lays the foundation for a child’s physical and neurological growth.
• Proper prenatal care, such as adequate nutrition and medical monitoring, is essential to support the formation of vital organs and brain development.