Birth and Post-natal Development

Unit 2

The Continuation of Life

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Unit 2: The continuation of life

Chapter 18:

Birth and Post-natal Development

Higher Human Biology

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What you need to know: The arrangements.Birth

• The role of oxytocin at birth and the use of artificial hormones in induction of birth.

• Nutrition of the new-born (Consideration of the nutrition of the new-born should include the presence of antibodies in colostrum and breast milk and some reference to the possibility of chemical contamination of colostrum and breast milk).

The pattern of growth after birth• The major stages of the growth curve, including changes in body proportions.• The role of growth hormone (The general effects of growth hormone on the

growth process should be considered, but microscopic details of bone structure or bone growth are not required).

• The major body changes in males and females at puberty.• Hormonal changes and development in males and females at puberty.

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Learning Intentions

Understanding how the embryo develops inside the uterus and effects that the uterine environment can have on this development

Success Criteria

• Explain the role of oxytocin at birth and the use of artificial hormones in induction of birth

• Describe how the new born infant is nourished

• To find out about the composition of colostrum

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Image source: images.doctorberlin.com

BirthBirth•A human pregnancy lasts for about 38 weeks. •After the full period of gestation when the foetus is described as ‘full term’. Gentle contractions of the uterus move the foetus into the birthing position, with the head close to the cervix (PATURITION).

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Anterior (front)

lobe

LabourLabourLabour is brought on by the hormone oxytocin, which is secreted by the mother’s posterior pituitary gland. This hormone stimulates involuntary rhythmic contractions of the uterine wall, which start at the top of the uterus and work their way downwards in waves.

During the early stages of labour the amniotic sac bursts (waters break) and the cervix gradually dilates (opens). The contractions become stronger and come more often until eventually the baby is expelled from the uterus and delivered through the vagina.19/04/23 6Mrs Smith Ch18 Birth & Post-

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Induced BirthInduced BirthNowadays, birth can be artificially induced by gradually injecting synthetic oxytocin (or a hormone which mimics its effect) into the mothers bloodstream.

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Birth: Summary!

Oxytocin:• Produced by pituitary gland.• Brings about uterine contractions

during labour.• stimulates contractions of mammary

gland muscle tissue resulting in milk ejection.

• Labour can be induced by injection of oxytocin.

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Nutrition of the NewbornNutrition of the NewbornLactationLactation

Following parturition (the baby getting into position for birth) the hormone prolactin the mothers mammary glands become enlarged ready to produce milk. For milk to be released from the breasts– lactation the hormone oxytocin must be released.

As well as stimulating the uterine contractions during labour, oxytocin stimulates contraction of muscle tissues in the mammary glands causing milk to be released.

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Nutrition of the Newborn Nutrition of the Newborn ColostrumColostrum

Colostrum “mother-milk” is a yellow liquid produced by mammary glands a few hours after birth.  It is the first milk the baby receives.

Colostrum is not only a source of protein, carbohydrate, fat, vitamins and minerals which are important for growth but it is also rich in maternal antibodies so gives the baby passive immunity against many diseases.

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A few days after birth normal breast milk is produced, which has fewer antibodies than colostrum but is richer in lactose sugar and fat.

Nutrition of the Newborn Nutrition of the Newborn

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If a baby it not breastfedSome mothers choose not to or find it too difficult to breast feed and instead feed their baby with powdered cow’s milk. This is also rich in the nutrients needed (especially proteins & minerals) by newborns. However this lacks the antibodies needed to protect the baby until it’s own immune system develops.

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Nutrition of the Newborn Nutrition of the Newborn Colostrum vs Normal MilkColostrum vs Normal Milk

Colostrum Milk Normal Milk

First Milk Few days after birth

Rich in maternal antibodies

Contains fewer maternal antibodies

Less lactose and fat Richer in lactose and fat

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FYI: Colostrums mature breast milk

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FYI – breast milk contains many more essential

vitamins and minerals to

support healthy

development

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Babies do not get an adequate supply of iron from milk. Instead, they make use of iron stored during gestation (pregnancy) until they begin to eat solid

foods at about 6 months.

Iron is an essential part of our diet because it is needed to: Foods

rich in iron:

• Make many enzymes (e.g. catalase)

• Make cytochrome (for aerobic respiration)

• Form part of the haem group in haemoglobin

Nutrition of the NewbornNutrition of the NewbornIronIron

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Contamination of Breast MilkContamination of Breast MilkOrganochlorides.Organochlorides.

• Organochlorides are non-biodegradeable chemicals used in pesticides on crops.

• These can increase in concentration along the food chain and so are abundant in the final consumers (e.g. large fish, birds of prey, humans).

• Stored in fatty tissue (these molecules are fat-soluble) including breast milk!

Excessive concentrations of these chemicals have been found in breast milk (so high it exceeds legal limits for commercially produced foodstuffs), fortunately there are no known cases of babies becoming ill from this. Many of these chemicals (e.g. DDT) are now banned in many countries

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A mini-clip: DDT in umbilical cords, it’s not a giant leap to assume there is traces in breast milk!

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Nutrition: Summary

• Prolactin stimulates lactation Oxytocin is needed to release the milk.

• Colostrum – first milk. Yellowish fluid rich in antibodies.

• Normal breast milk – fewer antibodies, rich in lactose and fat. May contain organochlorides from mother’s diet

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Task: Torrance-TYK pg131 Qu’s 1&2

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Task: Torrance AYK pg135 Qu’s 1

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Learning Intentions

Understanding the pattern of growth after birth and the influences of hormones on this.

Success Criteria• Plot and interpret a human growth

curve

• Stat that body proportions vary through development from foetus to adult

• Explain the role of growth hormone during normal development and the consequence of underproduction /overproduction. To study the effects of steriod use

• Summarise

– The major changes in males and females at puberty.

– The hormonal changes in males and females at puberty.

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Growth After BirthGrowth After BirthMeasured as weight or height against time.

When graphed this is called a growth curve.

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Growth CurveGrowth CurveWhen drawn as a graph, growth takes the form of a

curved line, thus is called a growth curve. It contains two phases of rapid growth called growth spurts! This is a

sigmoid (S-shaped) curve.

Time

Units of growth

e.g. Fresh mass, height

Accelerating growth

Decelerating growth

Steady rapid growth

No growth

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Human Growth: Human Growth: 2 main growth spurts2 main growth spurts

Growth spurt (0-2

years)

Growth spurt at puberty

Slight loss of mass after

birth

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Accelerating growth: Each daily increase is greater than previous.

Steady rapid growth: Daily increase remains constant.

Decelerating growth: Growth continues but each days growth is less than the previous days.

*Exam tip: if describing graphs, include values in your answer!

Growth PatternsGrowth Patterns

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Body ProportionsBody ProportionsBody proportions change as we grow from an embryo into an adult.

Head of a baby = 25% of body lengthHead of an adult = 13% of body length

The new-born baby’s lowers limbs = 33% of body lengthAn adults lowers limbs = 50% of body length

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Growth

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The brain normally approaches adult size on the fifth year. The sex organs remain dormant until

adolescence.

Human Growth Hormone (GH) = Human Growth Hormone (GH) = AKA SOMATOTROPIN. AKA SOMATOTROPIN.

Pituitary gland

Hormones are chemical messengers, produced in the endocrine glands (e.g. pituitary gland) then secreted into the bloodstream.

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somatotrophin

Anterior (front)

lobe

Produced in the anterior lobe of the pituitary gland.

Human Growth Hormone: aka Human Growth Hormone: aka Somatotrophin.Somatotrophin.

• Somatotrophin - human growth hormone Somatotrophin - human growth hormone secreted by the anterior pituitarysecreted by the anterior pituitary

• The growth spurt which takes place during adolescence is due to an increased production of GH.

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Human Growth Hormone (GH) = Human Growth Hormone (GH) = AKA SOMATOTROPIN. AKA SOMATOTROPIN.

Human Growth Hormone (GH) = Human Growth Hormone (GH) = AKA SOMATOTROPIN. AKA SOMATOTROPIN.

Promotes growth by • Accelerating amino acid transport into

bone and soft tissue cells.– This in turn particularly enhances

growth of bones (especially the long bones of the body in the arms and legs) and cartilage.

• Stimulating the breakdown of fats for energy release allowing rapid synthesis of proteins.

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Pituitary Dwarfism

• An under-production of GH during adolescence leads to a reduction in growth

• Nowadays if a child is diagnosed with this condition they can be treated.

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Pituitary Dwarfism in the German Shepherd Dog

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Treatment for DwarfismTreatment for DwarfismAs the production of somatotrophin is controlled by a gene, scientists have used genetic engineering to transfer this gene into a bacterium to produce human growth hormone. The hormone is then extracted and used to treat children who show the early signs of pituitary dwarfism.

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Giantism

• An over-production of GH during adolescence leads to an abnormal increase in growth, especially in the long bones.

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Acromegaly• Acromegaly occurs in about 6 of

every 100,000 adults. It is caused by abnormal production of growth hormone after the skeleton and other organs finish growing.

• Growth hormone normally decreases once adolescence is completed.

• If excessive GH production occurs in adulthood, an abnormal increase in the bones of the hands, feet and jaw (not the long bones) occurs

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Body Changes at PubertyBody Changes at PubertyThe second growth spurt occurs at puberty.

Until this stage the sex organs remain dormant, at puberty the sex organs become functional and a child changes into an adult. Males tend to reach puberty later than females. During puberty the body changes to develop secondary sexual characteristics.Primary sexual characteristics (e.g. possession of male/female genitals) occur at birth19/04/23 38Mrs Smith Ch18 Birth & Post-

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Secondary sexual characteristics – happen during adolescence/puberty

Changes in males Changes in femalesGrowth in height and weight

Growth in height and weight

Maturation of sex organs i.e. testes, scrotum and penis

Maturation of sex organs i.e. uterus, oviduct and vagina

Manufacture of sperm begins

Ovulation and menstruation begin

Increased growth of body hair

Increased growth of body hair

Deepening of voice Widening of hips and growth of breasts19/04/23 39Mrs Smith Ch18 Birth & Post-

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Hormonal Hormonal Changes at Changes at

PubertyPuberty

Production of sex hormones

hypothalamus secretes releaser hormone

transported in the bloodstream to the anterior pituitary gland

releases gonadotrophic hormones (FSH and LH, or ICSHtransported via

the bloodstream to the gonads

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GonadsGonadsThe gonads (ovaries &

testes) respond to

gonadotrophic hormones

Oestrogen & Progesteron

e

Testosterone

The sex hormones are steroid hormones:• fat soluble lipids• they can pass through cell membranes & switch on some of the targets cells genesDevelopment of secondary sexual

characteristics

Controls menstrual cycle19/04/23 41Mrs Smith Ch18 Birth & Post-

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Essay Questions:SQA 2008

Give an account of the development of boys at puberty under the following

headings:

(i) physical changes; (3)

(ii) hormonal changes. (7) (10)

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Essay Questions:SQA 2002

Give an account of the influence of hormones on the growth and development of boys.

(10)

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Steroids in SportSteroids in Sport

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Steroids in SportSteroids in SportAnabolic steroids = male sex hormones

(testosterone + man-made derivatives)

•Taken as pills or injection•Used to increase muscle mass + strength

Problems of overuse:• masculinisation in women• shrinkage of testes• reduced sperm production• temporary sterility (ICSH & FSH secretion is inhibited)• damage to liver, kidneys & heart• depression, aggression & antisocial behaviour

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Task: Torrance-TYK pg135 Qu’s 1&2

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Task: Torrance AYK pg126 Qu’s 2, 3, and 5

19/04/23 47Mrs Smith Ch16 Intervention in fertility