Fertilization, Pregnancy & Birth

Fallopian tube Fimbria Ovary Uterus Endometrium Cervix Vagina

Uterus: The hollow pear-shaped organ located between the bladder and the anus in females Endometrium: The glandular inner lining of the uterus Fallopian Tube: The tubes that connect the ovary to the uterus Fimbria: The fingerlike projection at the end of the fallopian tube Vagina: The muscular canal extending from the cervix to the outer environment also known as the birth canal Cervix: The muscular band that separates the vagina from the uterus

Sperm First Trimester weeks

0-1.5 weeks

Female Egg weeks

Fertilization

Zygote: Completion of the secondary oocyte, receives 23 chromosomes

Cleavage: Cleavage: The cell division of a zygote without changing the original size of the zygote weeks

Early Cleavage weeks

Late Cleavage weeks

Blastocyst: Blastocyst: The early stage of embryo development weeks

Implantation: Implantation: The attachment of the embryo to the endometrium weeks

Endometrium Yolk Sac: Yolk Sac: site of early red blood cell formation Chorion Amnion Embryo Allantois Umbilical Cord Connects fetus to the placenta 1.5 weeks

Surrounding Membranes Chorion: The outer extra embryonic structure of a developing embryo that will contribute to the placenta, which produces hCG Amnion: The fluid filled extra embryonic structure Allantois: The extra embryonic structure that contributes to the blood vessels of the placenta, which provides an exchange between the mother and the fetus.

Placenta Umbilical Cord Amnion Chorion 1.5 weeks Exchange of nutrients and waste from mother to fetus

Gastrulation: Process by which a gastrula is formed Ectoderm Mesoderm Endoderm

Gastrula Layers Ectoderm: skin, hair, fingernails, sweat glands nervous system, brain, peripheral nerves inner ear, cochlea, semicircular canals teeth, inside lining of mouth Mesoderm: muscles, skeletal and smooth blood vessels and blood kidneys, reproductive structures connective tissue, cartilage, bone Endoderm: liver, pancreas, thyroid, parathyroid urinary bladder lining of digestive system lining of respiratory tract

2 nd & 3 rd week -Formation of primitive steak and primary germ layers -Central nervous system begins to develop -Heart development initiated; beating begins

4 th week - Early eyes develop - -limb buds of arms and legs develop

5 th week -Nose and lip formation begins -Architecture of brain and spinal cord are established

6 th -8 th week -Hands and feet are now visible -Baby begins to be active to the surrounding environment -Masculine development in males although no change in females

9 th -12 th week -Fetal development begins -Placenta well established and now weighs more than baby

Second Trimester 14 th -16 th week - Baby can suck swallow and make irregular breathing movements - Fetal heart beat can be heard with amplification - Fetal movement is recognized - Sex is now distinguished

17 th -20 th week -Fine hair covering over entire body -Fetal heart beat heard

Third Trimester 28 th week - Baby can survive outside uterus if lungs are capable of breathing - 10%-20% survival if baby is born at this time

32 nd week -Beginning of head turning down -Skin appears red and wrinkly at this time

34 th -40 th week -Baby same size as placenta -Fingernails now visible at the tip of fingers -Full term

Full process

Birth Water Breaks

Cervix Dilates

Baby makes their way out

Placenta exits right after baby

Umbilical Cord is cut

Baby Is Born!!

Human sex determination Females have two X chromosomes, where as males have one X and one Y. These chromosomes will identify the male and female phenotype. A fetus can only be determined until the sixth or seventh week of pregnancy, in this event the sex-determining region of the Y chromosome will develop a gonad into a male testis. This directs the development of male characteristics. Though, the absence of the sex- determining region of the Y chromosome will lead to the development of female characteristics.

Role of hormones in Pregnancy Relaxin: Relaxin: produced by the placenta, to loosen ligaments in pelvis Oxytocin: Oxytocin: Produced by pituitary, causes strong uterine contractions to push baby out of vagina. Prolactin: Prolactin: Produced by pituitary, and is associated with the production of milk.