Human Development

Timeline created by kristen3939
  • Day 1 of Gestational

    Day 1 of Gestational
    Day 1 of Gestational Day: Menstrual Phase
    Menstrual cycle changes, uterus endometrium is lost, ovary follicle is developed. Endocrine changes during pregnancy block the menstrual cycle, which normally would shed the functional layer of the uterine lining each cycle.
  • Day 5 of Gestational

    Day 5 of Gestational
    Day 5 of Gestational Day: Proliferative Phase
    Menstrual cycle changes, uterus endometrium proliferative, ovary follicle develops.
    Second phase of the uterine cycle when estrogen causes the lining of the uterus to grow, or proliferate, during this time. As they mature, the ovarian follicles secrete increasing amounts of estradiol, and estrogen.
  • Day 14 of Gestational

    Day 14 of Gestational Day: Ovulation Capacitation
    Menstrual cycle has late proliferative.
    Sperm must undergo the process of capacitation in order to have the “capacity” to fertilize an oocyte. If they reach the oocyte before capacitation is complete, they will be unable to penetrate the oocyte’s thick outer layer of cells.
  • Day 1 of Fertilization

    Day 1 of Fertilization
    Secretory Phase: Stage 1
    Fertilization, zygote, Secretory Phase
    Progesterone stimulated by LH is the dominant hormone during this phase to prepare the corpus luteum and the endometrium for possible fertilized ovum implantation.
  • Day 3-5 of Fertilization

    Day 3-5 of Fertilization: Stage 3
    Blastocyst hatches ( zona pellucida is lost), late secretory, blastocyst is free floating.
    This hatching allows increased growth, access to uterine nutrient secretions and blastocyst adhesion to the uterine lining.
  • Day 6-7 of Fertilization

    Day 6-7 of Fertilization
    Day 6-7 of Fertilization: Stage 4 and 5
    Day 6: Adplantation
    Day 7: Implantation
    Implantation is an early stage of pregnancy. It happens when a fertilized egg attaches to a woman's uterus. Implantation is the stage of pregnancy at which the embryo adheres to the wall of the uterus. At this stage of prenatal development, the conceptus is called a blastocyst. It is by this adhesion that the embryo receives oxygen and nutrients from the mother to be able to grow.
  • Day 16-20 of Fertilization

    Day 16-20 of Fertilization: Stage 7 and 8
    Day 16- gastrulation, ectoderm, mesoderm and endoderm form
    Day 18- neural neurogenesis, neural groove and folds are first seen
    Day 20- first somites are formed and continued to be added to the sequence, three main divison of brain begins (which are not cerebral vesicles), neural crest is visible.
  • Day 22 of Fertilization

    Day 22 of Fertilization
    Day 22 of Fertilization: Stage 10
    Neural Crest differentiation at spinal cord, neural folds begin to fuse near the junction between brain and spinal cord, Neural Crest cells are arising mainly from the neural ectoderm, trigeminal, facial, and postotic ganglia components visible, migration of vagal level neural crest cells begins
  • Day 23 of Fertilization

    heart begins to beat, first functioning embryonic organ formed.
  • Day 25 of Fertilization

    Day 25 of Fertilization
    liver septum transversum forming liver stroma and hepatic diverticulum forming hepatic trabeculae, caudal neuropore takes a day to close, secondary neurulation begins, onset of the ventricular system and separates the ependymal from the amniotic fluid, cardiac crest, neural crest from rhombomeres 6 and 7 that migrates to pharyngeal arch 3 and from there the truncus arteriosus, vagal neural crest enter the foregut.
  • Day 27-29 of Fertilization

    Day 27: the neural tube is normally completely closed, ventricular system now separated from amniotic fluid. Neural crest at spinal level is segregating, and spinal ganglia are in series with the somites. Spinal cord ventral roots beginning to develop
    Day 28: Crest comes from the nasal plates, vision, and diaphragm begins forming
    Day 29: respiratory and hearing begins forming
  • Day 32 of Fertilization

    Day 32 of Fertilization
    sensory placodes, lens pit, otocyst, nasal placode, primary/secondary vesicles, fourth ventricle of brain, heart prominence, 1st, 2nd and 3rd pharyngeal arch, forebrain, site of lens placode, site of otic placode, stomodeum. Body - heart, liver, umbilical cord, mesonephric ridge visible externally as bulges.
    limb upper and lower limb buds growing, mesoderm of the primary body wall coalesced in the ventral midline to create the abdominal cavity, first appearance of the future cerebral hemispheres
  • Day 35-37 of Fertilization

    retinal pigment present, connecting stalk between pouch and oral cavity degenerates, descent of heart and lungs into thorax, first parasympathetic ganglia, submandibular and ciliary, are identifiable, development of the middle cerebral artery is first identified as small buds, present of eyelids begins forming
  • Day 41 of Fertilization

    Day 41 of Fertilization
    olfactory nerve fibres enter the brain, sulcus (groove) above and below eye deepen and eyelid folds develop, heart seperation of common cardiac flow
  • Day 43 of Fertilization

    pancreatic hormones secretion increases, small amount maternal insulin, enlargement of liver stops descent of heart and lungs, replacement of cartilage with bone
  • Day 48 of Fertilization

    Day 48 of Fertilization
    eyelid folds develop into the eyelids and cover more of the eye as the palpebral fissure takes shape, cardiovascular/respiratory system develops, genital develops, musculoskeletal develops.
  • Day 49-50 of Fertilization

    scalp vascular plexus visible, limb upper limbs begin to rotate ventrally, formation of the anterior communicating artery, limbs begin rotating
  • Day 53 of Fertilization

    Day 53 of Fertilization
    fingers and toes lengthen
  • Day 55 of Fertilization

    defines the end of the embryonic (organogenesis) period, heart prominence, ossification continues, Head nose, eye, external acoustic meatus, eyelids, external ears, rounded head Body - straightening of trunk, umbilical cord, intestines herniated at umbilicus limb upper limbs longer and bent at elbow, hands and feet turned inward, foot with separated digits, wrist, hand with separated digits