week 1 Flashcards
Genetic transmission
Nuclei of reproductive cells contain 23 chromosomes
Special form of cell division in reproductive cells = meiosis
Mitosis
For regeneration/ growth
Meiosis
Produces egg and sperm
process of fertilisation
egg + sperm= Zygote-> embryo
Conception genetic
Gametes: reproductive cells egg and sperm only contain half material
Meiosis: Cell division that produces gametes
Conception: the union of an egg from the mother and a sperm from the father fertilisation
Zygote: a fertilised egg cell
How do twin develop
Identical twin: Twins that result the splitting in half of the zygote
Each of the two resulting zygotes have exactly same set of genes
Fraternal twins: Twins that result when two eggs happen to release in fallopian tubes at the same time
Fertilised by two different sperm
Fraternal twins have only half of their genes in common
Journey of the egg
Step 1- egg leaves ovary and enters fallopian tubes
Step 2- sperm enters egg and unites with nucleus
Step 3: fertilised egg divides
Step 4- cells attach to uterus
Germinal stage
conception- 2 weeks
From conception until implantation in the wall of the uterus
0-2 weeks from conception: Zygote travels down fallopian tube too uterus
Cells multiply rapidly: from 2 cells at 36 hours post fertilisation to 76-0 cells 5 days later
When zygote reaches uterus, tendrils emerge and it burrows into uterine lining
Begins to use mothers blood supply. Cell differentiate as they multiply
Embryonic stage
2 weeks-8 weeks
Period of rapid cell division and differentiation, during which embryo takes on recognisably human shape.
Three key structures emerge from fertilised egg: Amniotic sac, placenta, umbilical sac
Organism divides into 3 layers. ectoderm hair, teeth, outer skin layer, Ns
Mesoderm: inner skin layer, skeleton, muscles
Endoderm: vital organ, glands, gastrointestinal tract
Foetal stage
8 weeks- 38 weeks
Period of continuous growth for major structures and systems, culminating in birth
Major feature= brain development around 4 months gestation mothers begin to feel gestation mothers begin to feel foetal movement
Around 5 months gestation reflexes emerge
Around 6 months gestation foetus may be viable
Amniotic sac
A transparent fluid-filled membrane that surrounds and protects the foetus
Placenta
A support organ for the foetus that permits the exchange of materials carried in the bloodstream of the foetus and mother
Umbilical cord
A tube containing the blood vessels connecting the foetus and the placenta
Development processes
Mitosis:: cell division resulting in two identical daughter cells
Cell migration: newly formed cells move away from point of origin
Cell differentiation: cells start to specialise in structure and function
Apoptosis: genetically programmed cell death
Foetal experience and behaviour
Movement: Foetal movement starts 5 to 6 weeks after conception. Emergence of hiccups, swallowing. Movement limbs, fingers. Respiratory readiness for breathing independently after birth
Behavioural cycles: Rest-activity in latter half of prenatal period. Circadian rhythm apparent. REM during active sleep
Sight: Minimal, foetal preferences.
Touch: contact with parts of the body; grasping umbilical cord, rubbing face, sucking thumb
Smell: amniotic fluid takes an odor from what mother eats phylogenetic continuity
Hearing: responds to various sounds from at least 6 months
