Postnatal Development Development During Infancy Dr Salim Khan

1. 1 Postnatal Development Development During Infancy Dr Salim Khan

2. 2 Learning Objectives By the end of today’s session, you should be able to: Explain how development of the nervous system continues during the postnatal period Identify how postnatal development contributes to development of motor skills during infancy Identify examples of and explain the influence of endocrine and nutritional factors on growth

3. 3 Infancy: stage of human development lasting from birth to approximately two years of age. Hallmarks of infancy are: - physical growth - motor development - vocal development - cognitive and social development.

4. 4 Changes in foetal circulation at birth. See diag. Stimuli: 1. Suspension of placental circulation increases peripheral resistance 2. Powerful inspiratory muscular movements decrease resistance in pulmonary circulation 3. Blood becomes more saturated with oxygen due to independent breathing.

5. 5 Postnatal Development of the Nervous System Not due to neurogenesis (development of new neurones) Factors that influence postnatal development of the nervous system - Role of myelination - Role of synaptogenesis

6. 6 Neurones Neurones increase in size. Neurones become coated with MYELIN, a fatty substance Helps speed neural impulses Process incomplete until puberty The brain is made up of neurons, and triples its weight in the first two years of life. The infant's brain is 3/4 its adult size by age two

7. 7

8. 8 Babinski's sign (Plantar Sole reflex) Tests integrity of spinal cord from L4-S2 Babinski's sign is associated with upper motor neuron lesions anywhere along the corticospinal tract affecting the lower extremities. Normal response is a downward flexion (curling) of toes If corticospinal tract damaged, normal plantar’s reflex replaced by Babinski’s sign Toes fan backwards

9. 9 The Developing Brain The early brain has 3 parts, the hindbrain, midbrain, and forebrain In each part of the brain, structures develop that facilitate maturation of the brain - Hindbrain structures - Midbrain structures - Forebrain structures

10. 10 Motor Development in the year after birth Birth – suckles 1 month – smiles 2 months – vocalises 4 months – hand control 6 months – sits briefly 9 months – pulls up 12 months – walks

11. 11 Newborn Reflexes At birth, extensive repertoire of innate behaviours Unlearned, organised involuntary responses that occur automatically in response to specific stimuli - sucking reflex - rooting reflex - moro reflex

12. 12

13. 13 Physiological Basis of Growth Growth is due to an increase in the size of organs and tissues Growth occurs by mitosis and hypertrophy Nutritional Influences on Growth - Proteins - Lipids - Vitamins - Minerals

14. 14 Nutrition in Infancy Fuels Motor Development Nutrition during infancy is extremely important! Without proper nutrition, infants cannot reach their physical potential and also may suffer cognitive and social consequences. Malnutrition & It’s Effects Malnutrition, the condition of having an improper amount and balance of nutrients produces several results. - slower growth - susceptibility to disease - lower IQ scores (Risks of malnutrition are greater in underdeveloped countries and in areas with high poverty rates. Under nutrition is more common in developed countries (deficiency in the diet).

15. 15

16. 16

17. 17 Endocrine Influences on Physical Growth Growth Hormone – influences growth of bone GH stimulates release of Insulin – like growth factors that in turn stimulate cartilage and bone growth Thyroid hormones – important for actions of growth hormone and development of the nervous system TH must be present for GH to exert its action

18. 18 The first year is characterized by rapid physical growth. A normal baby doubles its birth weight in six months and triples it in a year. During that time, there is great expansion of the head and chest, thus permitting development of the brain, heart, and lungs, the organs most vital to survival. The bones, (relatively soft at birth), begin to harden, and the fontanelles, (the soft parts of the newborn skull), begin to calcify

19. 19

20. 20 The skull is made up of many bones, 7 in the skull itself and 14 in the facial area. They join together to form a solid, bony cavity protecting the brain and supporting the structures of the head. The areas where the bones join together are called the sutures. The bones are not joined together firmly at birth. This allows the head to accommodate passage through the birth canal. The sutures gradually accumulate minerals and harden, firmly joining the skull bones together. This process is called ossification. In an infant, the spaces where two sutures intersect form a membrane-covered "soft spot" called a fontanelle (fontanel). The fontanelles allow for growth of the skull during an infant's first year.

21. 21 Small one at the back of the head at about 3 months, the larger one in front at varying ages up to 18 months. Brain weight also increases rapidly during infancy: by the end of the second year, the brain has already reached 75% of its adult weight.

22. 22 Growth and size depend on environmental conditions as well as genetic endowment. E.g. severe nutritional deficiency during mother's pregnancy and in infancy are likely to result in an irreversible impairment of growth and intellectual development Overfed, fat infants are predisposed to become obese later in life. Human milk provides basic nutritional elements necessary for growth (see later). In Western cultures supplemental foods are generally added to the diet during the first year.

23. 23 Colostrum is the first milk your breasts produce in the early days of breastfeeding. This special milk is low in fat, and high in carbohydrates, protein, and antibodies to help keep your baby healthy. It is extremely easy to digest, and is therefore the perfect first food for your baby. It is low in volume but high in concentrated nutrition for the newborn. Colostrum has a laxative effect on the baby, helping him/her pass early stools, which aids in the excretion of excess bilirubin and helps prevent jaundice.

24. 24 Colostrum provides not only perfect nutrition for newborn, but also large amounts of living cells which will defend baby against many harmful agents. The concentration of immune factors is much higher in colostrum than in mature milk. Colostrum actually works as a natural and 100% safe vaccine. It contains large quantities of an antibody called secretory immunoglobulin A (IgA) which is a new substance to the newborn. Before baby is born, received benefit of another antibody, IgG, through placenta. IgG worked through the baby's circulatory system, but IgA protects the baby in the places most likely to come under attack from germs, namely the mucous membranes in the throat, lungs, and intestines.

25. 25 Colostrum has an especially important role to play in the baby's gastrointestinal tract (GIT). A newborn's intestines are very permeable. Colostrum seals the holes by "painting" the GIT with a barrier which mostly prevents foreign substances from penetrating and possibly sensitizing a baby to foods the mother has eaten. Colostrum also contains high concentrations of leukocytes, protective white cells which can destroy disease-causing bacteria and viruses. Concentrations of antibodies in milk lower in mature milk. Baby will be taking in much higher volumes of milk. The disease-fighting properties of human milk do not disappear with the colostrum. In fact, as long as baby receives your milk, baby receives immunological protection against many different viruses and bacteria.

26. 26 Renal Function The newborn has an immature kidney, and can maintain water and electrolyte balance only within a fairly narrow range of intakes and losses. The functional development of the nephron is not complete until 1 month of age. The tubules are short and narrow and do not reach mature proportions until approximately 5 months. In addition, the pituitary gland produces only limited quantities of the antidiuretic hormone (ADH) vasopressin, which normally inhibits diuresis. These factors limit the newborn's ability to concentrate urine and to cope with fluid and electrolyte stress, i.e., electrolyte-dense formula, limited fluid intake, and diaorrhea.

27. 27 Sensitivity to Pain and Touch Infants are born with the capacity to feel pain. Touch is one of the most highly developed sensory systems in a newborn. The rooting reflex is strong. Present in normal full-term babies. If a baby comes into contact with the mother's breast then he 'roots' for milk. It is examined by lightly touching the corner of the baby's mouth. In response the baby lowers the bottom lip on the same side and his tongue moves towards the point of stimulation. Infants gain information about the world through touch. Even the youngest infants respond to gentle touches and are calmed by them

28. 28 Sensory Development Hearing Hearing well developed Turn head in direction of sound Notice changes in melodies and sounds A requirement for language Can differentiate their mother's voice from other voices

29. 29 Sensory Development Vision Born blind, develop normal vision by 6 months By 3-4 months recognise colours Infants show clear visual preferences that are present at birth Prefer to look at patterns and complex stimuli Prefer to look at faces (mothers rather than fathers; can you blame them!!)