Fetal Development PDF

CHAPTER 9: STAGES OF FETAL Normal ejaculation of semen: DEVELOPMENT 2.5 mL of fluid containing 20- 200 Million Pre- embryonic- first 2 weeks, beginning with spermatozoa per Milliliter or an average of 400 fertil...

CHAPTER 9: STAGES OF FETAL Normal ejaculation of semen: DEVELOPMENT 2.5 mL of fluid containing 20- 200 Million Pre- embryonic- first 2 weeks, beginning with spermatozoa per Milliliter or an average of 400 fertilization million sperm per ejaculation. Embryonic- weeks 3 though 8 Hyaluronidase- a proteolytic enzyme. Released by the spermatozoa and dissolves the layer of cells Fetal- from week 8 through birth protecting the ovum. After penetration of the ovum and TERMS TO DESCRIBE FETAL GROWTH spermatozoon fuse to form a zygote. Ovum: from ovulation to fertilization Graafian follicle of ovary is surrounded by a ring of polyssacharide fluid (Zona pellucida) and a Zygote: fertilization to implantation circle of cells (Corona radiata). Embryo: implantation to 5-8 weeks 46 chromosomes and 23 pairs ( 22 autosomes Fetus: 5-8 weeks until term and 1 sex chromosomes). Conceptus: developing embryo and placental Fertilization Journey: structures throughout pregnancy FALLOPIAN TUBE- ZYGOTE- MORULA - Age of viability: the earliest age which fetuses BLASTOCYST ( EMBRYOBLAST- embryo AND survived if they are born generally accepted as 24 TROPHOBLAST- placenta) = Implantation weeks or at the point a fetus weighs more than 500- IMPLANTATION 600. A zygote migrates over the next 3-4 days toward TRIMESTERS: the body of the uterus, aided by the concurrents 1st trimester- 0- 12 weeks initiated by the muscular contractions of fallopian tube. 2nd trimester- 13- 24 weeks cell divison occurs ( mitotic divison or cleavage ) 3rd trimester- 24- 40 weeks during implantation. first cleavage occurs during first 24 hours. FERTILIZATION Cleavage continue to occur at a rate of about one every 22 hours. FERTILIZATION- Referred to as conception and impregnation. zygote reaches the body of uterus consisting 16- 50 cells. is a union of an ovum and spermatozoon. From The Biology of Prenatal Development. Fertilization occurs at the outer third of the Script: fallopian tube, termed as ampullar portion ( ampulla of vater). MORULA VS. BLASTOCYST: An ovum is capable of fertilization for only 24 By 3 to 4 days after fertilization, the dividing cells of Hours ( 48 hours at most). the embryo assume a spherical shape and the embryo is called a morula. By 4 to 5 days, a cavity forms After 24- 48 hours it ( Ovum) atrophies and within this ball of cells and the embryo is then called becomes nonfunctional. a blastocyst. 5 days – is the functional life of spermatozoon Blastocyst: A rapidly dividing ball of cells and has 2 6 days ( 5 days before ovulation plus 24 hours rings. afterward)- Critical time span during sexual Embryoblast:known as the inner group of cells will intercourse must occur for fertilization to be become the embryo successful is 6 days. Trophoblast: known as the outer group will become in intervillous spaces of uterine endometrium the cells that nourish and protect it. surrounding chorionic villi. IMPLANTATION- contact between the growing 3rd week of pregnancy- oxygen and other nutrients structures and the uterine endometrium, occurs such as glucose, amino acids, fatty acids, minerals, approximately 8-10 days. vitamins, and water osmose from maternal blood through cell layers of the chorionic villi into villi Implantation occurs high in the uterus on the capillaries. From there nutrients are transported to posterior surface. developing embryo. once implanted, the zygote is called embryo. Placental transfer is dynamic: It allows all but few pregnancy ends as early 8-10 days after substances can only cross from the mother to fetus. conception Teratogens: any agent that causes an abnormality EMBRYONIC AND FETAL STRUCTURES following fetal exposure during pregnancy. Placenta and Membranes: serves as the fetal lungs, TERATOGENS MNEMONICS: kidneys and digestive tract in utero as well as help TORCH protection for fetus. T- oxoplasmos HCG: Human Chorionic Gonadotrophin is secreted by trophoblast cells and responsible for positive PT. O- ther agents ( Syphilis) Decidua: ( Latin word for falling off) The R- ubella ( Rubella is the German measles and endometrium is termed as decidua because it will be Rubeolla is the measles itself) discarded after birth. C- ytomegalovirus Chorionic Villi:occurs as early 11 or 12th day after H- erpes simplex ( HS1 and HS2) fertilization and appears resembling probing fingers. It reach out from the trophoblast cells into the uterine endometrium to begin formation of the TERATOWAS ( Medicines/ substances to avoid placenta. during pregnancy) Chorionic Villi has a central core that is composed T- halidomide (Can cause Amelia, a congenital of connective tissue and fetal capillaries surrounded absence of one or more limbs) by double layers of cells which produces placental hormones such as hCG, Somatomammatrophin E- pileptic Medication ( such as Valproic acid and ( Human placental lactogen (HPL) ), Estrogen, and Phenytoin) progesterone. R- etinoid ( Vitamin A) Cytotrophoblast: middle layer. Known as Langhans layer and it protects the growing embryo and fetus A- ce Inhibitors ( usually medication for agains infectious organisms in early pregnancy. hypertension or medicine that ends with -pril, arbs, and -sartan etc.) 20-24TH WEEK- Cytotrophoblast disappears and the layers have low protection and fetus are T- hird elements ( Lithium- given for those have vulnerable for viruses. mental disorders/ illnesses such as Bipolar patients etc.) Placenta: ( Latin for pancake) Grows from identifiable trophoblastic cells at the beginning of W- arfarin ( Anti-coagulant means anti-clotting). pregnancy to organ 15-20 cm in diameter. It provides A- lcohol oxygen and nutrients to the fetus. S- Sulfonamides ( Antibiotic) CIRCULATION- ( Involves circulatory system). Cotyledons:is a compartment that make maternal Placental circulation: occurs as early as 12th day of side of placenta look rough and uneven. pregnancy. Pregnant patients blood begins to collect  To provide enough blood exchange, the rate of Chorionic membrane:outermost layer and the 2nd uteroplacental blood flow of pregnancy membrane. Produces phospholipids that initiates increases from about 50 ml per minute at 10 formations of prostaglandins which triggers labor. weeks to 500-600 ml per minutes at term Amniotic membrane: or amnion, the innermost At term, placenta weights 400-600 g or 1 lb, layer forms beneath the chorion. A dual walled sac one-sixth of the weight of newborn. with chorion as the outermost part and the amnion as the innermost sac. Fused together, they have no Small placenta suggest compromised nerve supply so when they spontaneously rupture it circulation. While bigger placenta may indicate that is called the pregnant mother’s water breaks. the fetus was threatened and forced to spread out in unusual manner ( found usually in Amniotic Fuid: Amniotic fluid cushions and diabetic patient who is pregnant). protects the fetus during development in your uterus. It’s clear or light yellow and odorless. A fetus ENDOCRINE ( DUCTLESS GLAND) practices swallowing and breathing by drinking comes from outer layer of chorionic villi amniotic fluid.. Normally, it is from 800- 1,200 mL. ( syncytial). Secretes hormones. Hydramnios: excessive amniotic fluid Human Chorionic Gonadotrophin: HCG, a first Esophageal atresia or anencephaly: fetus is placental hormones to be produced. It is for positive unable to swallow. PT and can be found in urine and maternal blood. Oligohydramnios: reduction in amount of amniotic Pregnant person blood HCG will be negative for fluid. 1-2 weeks. No serum HCG after birth means no placental tissue is present in the uterus. Umbilical cord: Provides circulatory pathway that connects embryo to the chorionic villi. It transports Purpose of HCG: ensures that the corpus luteum of oxygen and nutrients to fetus from placenta and to ovary continuesbto produce progesterone and return waste products from fetus to placenta. estrogen so the endometrium of uterus is maintained. Progesterone: Hormone that maintain pregnancy. It is also necessary to maintain endometrial lining ORIGIN AND DEVELOPMENT OF ORGAN during pregnancy. SYSTEM Present in pregnant serum as early as 4th week of Stem cells pregnancy result of the continuation of corpus in first 4 days of life, zygote cells are term luteum. In 12th week or after placental Totipotent stem cells and it has potential to production begins progesterone rises grow in any kind of cell in the body. progressively. another 4 days, they lose ability to grow in any Estrogen: (Primarily estriol) a 2nd product of cells, instead they become a specific cell uch as syncytial cells of placenta. Contributes in mammary nerve, brain, or kin cells called Pluripotent cells. gland evelopment and preparation for lactation. in few days, cells grow so specific and termed as Human Placental Lactogen ( Human Chorionic Multipotent cells. Somatomammatrophin )- both a growth-promoting and lactogenic properties ( ex. Milk- producing). Zygote Growth: Development proceeds in a cephalocaudal ( head to tail) direction. Placental proteins: produces plasma protein, contributes in decreasing immunologic impact of growing placenta and help prevent hypertension of Germ Layers: pregnancy. Ectoderm: inner layer. Formed as CNS,PNS, skin, Amniotic membranes: a thin membrane on the hairs, nails, tooth enamel, sense organs, mucous inner side of the fetal placenta; it completely membrane of mouth, anus, and nose and mammary surrounds the embryo and delimits the amniotic glands. cavity, which is filled by amniotic liquid. Mesoderm: Middle layer. Supporting structures of PLACENTA( OXYGENATED BLOOD CAME the body ( connective tissues, bones, cartilages, FROM) – PASSES THROUGH FORAMEN muscle, ligaments, tendons), upper portion of urinary OVALE- TO RIGHT ATRIUM AND GOES TO system (kidneys and ureters), reproductive system, LEFT ATRIUM- TO DUCTUS ARTERIOSUS- heart, lynph, and circulatory systems and blood cells. (MIXING OF BLOOD HAPPENED)- THEN AFTER IT TRAVELS TO THE BODY- THEN Endoderm: Outer layer. Forms the Lining pf GOES BACK TO THE PLACENTA VIA AORTA. pericardia, pleura, and peritonial cavities, Lining of gastrointestinal tract, respiratory tract tonsil, AORTA: IS THE MAJOR ARTERY parathyroid, thyroid and thymus gland, and Lower urinary system ( bladder and urethra). CARDIOVASCULAR COMPOSITION: Organogenesis: organ formation. ( During this time in early organogenesis, the growing structure is most BLOOD (RBC, WBC, PLATELETS AND vulnerable to invasion by teratogens). PLASMA) CARDIOVASCULAR SYSTEM: The first system BLOOD VESSELS to become functional in intrauterine life. HEART Network of blood vessels and a single tube of heart forms as early of 16th day and beats as early RESPIRATORY SYSTEM as 24th day. 10th to 12 week, heartbeat may heard with a At 3rd week of intrauterine life, respiratory and doppler instrument. digestive tracts exists as single tube and it forms Electrocardiogram ( ECG) , May record a fetus as a sloid structure which then canalizes. heartbeat as early as 11th week but it is not that in 4th week, a septum begins to divide the accurate. esophagus and trachea. At the same time, lungs 28 weeks of pregnancy, sympathetic nervous buds appear on the trachea. system matures, heart rate stabilizes, and a 7th week, diaphragm does not completely divide consistent HR of 110- 160 bpm is assessed. the thoracic cavity from the abdomen and cause FETAL CIRCULATION: Fetus derives oxygen kung buds to extend down the abdomen, and excretes carbon dioxide not from gas exchange reentering the chest only. of lungs but from gas exchange in the placenta. Surfactant: a phospholipid substance excreted by NOTE: Blood arriving at fetus to placenta is highly alveolar cells of lungs at the 24th week of pregnancy. oxygenated. The blood enters the fetus through It decreases alveolar tension on expiration, prevent umbilical veins. alveolar collapse, and improving infants ability to maintain respirations in outside environment during FETAL CIRCULATION IS COMPOSED OF: birth. FORAMEN OVALE: allows oxygenated blood to enter right atrium to left atrium. DUCTUS ARTERIOSUS: carries oxygenated blood away from the lungs to aorta. 2 COMPONENTS OF SURFACTANT: LECITHIN AND SPHINGOMYELIN DUCTUS VENOSUS: carries oxygenated blood from placenta away from the semi functional liver Early formation of surfactant, sphingomyelin is towards the heart. the chief component. Septum valve: developed in 7th week Approximately 35 weeks, there is a surge in production of lechitin, which becomes the chief AVA- 2 ARTERIES AND 1 VIEN. component by a ratio of 2:1. STEP BY STEP FETAL CIRCULATION: Medulla oblongata:The bottom part of your THYROID GLAND: plays a major role in brainstem that regulates your breathing, heartbeat, chemical reactions in the body (our metabolism), as blood pressure and swallowing. well as our growth and development. The two main hormones your thyroid releases : thyroxine (T4) and triiodothyronine (T3) NERVOUS SYSTEM PARATHYROID GLAND: Releases Parathyroid Develops extremely in early pregnancy. hormone (PTH) is a hormone your parathyroid Neural plate: is apparent in 3rd week of gestation. glands release to control calcium levels in your blood. Top portion becomes neural tube that will form as It also controls phosphorus and vitamin D levels. If the CNS ( BRAIN AND SPINAL CORD) and your body has too much or too little parathyroid Neural crest which will develop into as a PNS. hormone, it can cause symptoms related to abnormal blood calcium levels. All parts of brain was developed but not matured enough. Brain growth continues at high Fetal adrenal glands supply a precursor level until 5 to 6 years. necessary for estrogen synthesis by placenta. Brain wave is detected through DIGESTIVE SYSTEM Electroencephalogram. It separates from the respiratory system tract Eye and inner ear develop as projection of about the 4th week of intrauterine life and after original neural plate that, begins to grow rapidly. 24 weeks, the ears is capable of responding to The proliferation of cells sheds in the second sounds and eyes exibit pupillary reaction. recanalization forms the basis for meconium. ENDOCRINE SYSTEM 16th week of intrauterine life, intestines becomes too large to be contained by the abdomen. The function of the organ begins along with neuro Therefore, the portion of intestine is pushed system development into the base of umbilical cord where it remains ADRENAL GLANDS:produce hormones that help until 10th week of IUL. regulate your metabolism, immune system, blood Intestine must rotate 180 degrees, if not it could pressure, response to stress and other essential possibly lead to volvulus ( Abnormal twisting of functions intestines) of the intestine of the newborn. PARTS OF ADRENAL GLANDS: Meconium : a collection of cellular wastes, bile, fats, Cortex and Medulla mucoproteins, mucopolyssacharides, and portion of the vernix caseosa accumulates as early as the 16th It consists of three layers: week. Zona glomerulosa (outer layer)- for sugar and 32 weeks: maturation of the swallowing reflexes and cortisol ( stress hormone) sucking ( Yet still not strong until the fetus is in full Zona fasciculata (middle layer)- for salt and term). Fetus also weighs about 1,500 g. aldosterone. 37 weeks: the gastrointestinal tract secretes enzymes Zona reticularis (innermost layer)- for androgen essential for protein and carbohydrate digestion found in saliva. Fetal pancreas produces insulin and also glucagon. Amylase : enzyme that breakdown carbohydrates ( but not mature until 3 months after birth). Insulin:decreases and regulate blood sugar Lipase: Enzyme for fat digestion. Glucagon:increases blood sugar levels. Thyroid and Parathyroid gland plays vital roles in fetal metabolic function and calcium balance. 2 serious problem that may occur in the first 24 INTEGUMENTARY SYSTEM hours of birth: Skin if the fetus appears thin and almost Hypoglycemia ( LOW BLOOD SUGAR) translucent until fat begins to be deposited underneath it about 36 weeks. Hyperbilirubinemia ( EXCESSIVE BREAKDOWN PRODUCTS FROM Lanugo: soft downy hairs that serves insulation to DESTROYED RBC). preserve warmth in utero. skin is covered by lanugo, a cream cheese like substance, vernix caseosa ( important for MUSCULOSKELETAL SYSTEM lubrication and keeping skin from macerating in FIRST 2 WEEKS OF FETAL LIFE- cartilage utero. Both lanugo and vernix is present at birth. prototypes provide position and support to fetus. 12th week to adulthood- ossification of cartilage IMMUNE SYSTEM into bones begins. IMMUNOGLOBULIN or IgG: maternal Fetus can be seen moving ( called quickening) in antibodies cross the placenta into fetus as early as ultrasonography by 11th week, although this not 20th week and at 24th week it give a temporary felt during pregnancy until 16th to 20th weeks of passive immunity against diseases for which mother gestation. has antibodies. Fetus only becomes capable of active antibody REPRODUCTIVE SYSTEM production late in pregnancy. Child sex can be determined and can be certain The following are five types of immunoglobulins in as early as 8th weeks by chromosomal analysis or humans: at 10th weeks with analysis of fetal cell in the mothers bloodstream. 6th week of implantation- gonad was form. If testosterone is secreted, it influences the sexually neural genital duct to form other male organs ( Maturity of wollfian or mesonephric duct). Absence of testosterone secretion a female organ will form ( maturation of Mullerian or paramesonephic duct). 34th- 38th week :testes formation in abdominal cavity and does descend in scrotal sac. MILESTONES OF FETAL GROWTH AND DEVELOPMENT Cryptorchidism: testes that do not descend. Fetus is typically measured from time of ovulation or fertilization URINARY SYSTEM the length of pregnancy is measured from 1st day of the last menstrual period ( gestational age). 12TH week, Urine is formed and excreted into the amniotic fluid by the 16th week of gestation. Both ovulation and gestational age are reported in lunar months. urine is excreted at rate of 500 ml per day. Note: loop of henle is not fully developed and glomelular filtration and concentration of urine 3 trimesters, 10 lunar months, and 280 days in in newborn is still not mature. pregnancy.  A fetus grows in utero for 9.5 lunar months or 3 - sex is distinguishable on outward appearance full trimesters (38 weeks or 266 days). - urine secretion begins but not yet evident in L :MEANS LENGTH amniotic fluid W :MEANS WEIGHT - heartbeat is audible through doppler technology END OF 4TH GESTATIONAL WEEK END OF 16TH GESTATIONAL WEEK - embryo L: 0.75 cm and W: 400 g. - Fetus L: 10-17 CM AND W: 55 to 120 grams - spinal cord is formed and fused in midpoint - Fetal heart is audible in ordinary stethoscope. - head is large and one third of entire structure -lanugo is well formed -rudimentary heart appears as prominent bulge on -pancreas and liver functions. anterior surface - Fetus actively swallows amniotic fluid, - arms and legs are bud like structure, rudimentary demonstrates intact but uncoordinated swallowing eyes, ears and nose are discernable reflex and urine is present in amniotic fluid. -sex is determined by Ultrasonography. END OF 8TH GESTATIONAL WEEK END OF 20TH GESTATIONAL WEEK - L: 2.5 cm and W: 20 g - L: 25 cm and W: 223 g - organogenesis is complete - movements of fetus can be felt by the mother - facial features( is discernable), arms and legs have -antibody production ( IgG) developed -Hair formation ( eyebrows, hair in head, and vernix - Heart ( w septum and valve) beats rhythmically. caseosa ) covers the skin. - facial features and arms and legs are discernable and - meconium( the feces or stool of the fetus) in the developed. upper intestine -Formation of external gentalia but sex is NOTE: Meconium becomes abnormal if: undetermined -A fetus is more likely to aspirate meconium if your - abdomen bulges forward because fetal intestine pregnancy goes beyond 40 weeks grows rapidly - it causes Meconium staining. Meconium-stained - a sonogram shows gestational sac, which is amniotic fluid is often caused by fetal hypoxia or diagnostic of pregnancy other physiologic stress. Any reflexive "gasping" of the unborn fetus, due to hypoxia, can depress the fetal diaphragm mechanically, squeezing the contents END OF 12 GESTATIONAL WEEK ( 1ST of the bowels into the amniotic fluid. ( Can cause TRIMESTER) aspiration). - Length of 7-8 cm and W: 45 g. -Presence of brown fat to regulate temperature. It forms in kidney, sternum, and Posterior neck - Nailbeds formation -Definite sleeping and activity patterns are -Presence of spontaneous movement of the fetus distinguishable - reflexes, such as Babinski reflex are present Note: Circadian Cycle- is responsible for wake-sleep -Bone ossification formation pattern or behavior. - tooth buds are present -Circadian rhythms are mostly affected by light and -fetus responds to sound by moving. darkness and are controlled by a small area in the - Active moro reflex ( being startled or makuratan ) middle of the brain. ( when born) - storing of iron END OF 24TH GESTATIONAL WEEK ( 2ND TRIMESTER) - fingernails reach the end of fingertips - L: 28-36 And W: 550 g - meconium is far from rectum END OF 36TH GESTATIONAL WEEK - Active production of lung surfactant - L: 48-52 CM AND W: 1,800- 2,700 ( 5-6 lb) -eyelids that is fused in 12 weeks opened and pupils -Body stores glycogen, iron, carbohydrates, and react to light. calcium - hearing can be demonstrated by response to sudden - additional subcutaneous fat is deposited sound -Sole of foot have one or 2 crisscross creases - Achieved the low end age of viability. NOTE: The absence of the crisscross creases implies that the newborn baby have a genetic condition :DOWN SYNDROME. END OF 28TH GESTATIONAL WEEK - lanugo begins to diminished - L: 35-38 cm and W: 1,200 g - most fetuses turn into vertex 9 head down) - Lung alveoli is almost matured, lung surfactant presentation. demonstrated in amniotic fluid END OF 40TH GESTATIONAL WEEK ( 3RD - testes begin to descend into scrotal sac from lower TRIMESTER) abdominal cavity - L: 48-52 cm and W: 3,000 g ( 7 – 7.5 lb) NOTE: - fetus kicks actively If the testes did not descend, it can cause Cryptorchidism. - fetal hemoglobin begins its conversion to adult hemoglobin Cryptorchidism- a condition in which one or both of the testes fail to descend from the abdomen into the - Vernix caseosa decreases after infant reaches 37 scrotum. weeks and more apparent in the creases than covering the body as the infant approaches 40 weeks - Blood vessels in retina are formed but thin and onwards. susceptible to damage to high oxygen - fingernails extends over fingertips NOTE: - creases on the soles of the feet cover at least two- Too much oxygen in fetus or also in newborn can thirds of the surface. cause blindness. Terms: PERRLA is an acronym for QUICKENING : is when a pregnant person starts “pupils are equal, round and reactive to light to feel their baby's movement in their uterus (womb). and accommodation.” Healthcare providers use the PERRLA eye test to check if your pupils look LIGHTENING: At the end of the third trimester, and function as they should. the fetus settles, or drops lower, into your pelvis. This is known as dropping. It may also be called END OF 32ND GESTATIONAL WEEK delivered a baby, dropping usually occurs 2 to 4 - L: 38 to 43 cm and W: 1,600 g weeks before delivery, but it can happen earlier. -subcutaneous fats begins to be deposited DETERMINATION OF ESTIMATED DATE ( based on what was being discussed) HEIGHT OF FUNDUS MEASUREMENT 1. NAEGELE’S RULE: measures the Last AND LOCATION ( McDonald Rule) menstrual period (LMP): The LMP calculation uses 12 weeks- At symphysis pubis the standard method of the first day of your last menstrual period plus 280 days to calculate the due 16 week- in between the symphysis pubis and date. umbilicus Calculation rules: 20 weeks- at the umbilicus - ALWAYS COVERT MONTH, DAYS, AND 24 weeks- 2 cm above umbilicus YEAR INTO NUMERICAL FORM ( EX. 09/11/ 2024) 28 weeks- in between the umbilicus IF : JAN- MAR 30 weeks- midway between umbilicus and xiphoid process - ADD 9 IN MONTH 34 weeks- 2 fingers below the xiphoid process - ADD 7 IN DAY 36 weeks- at the xiphoid process - AS IT IS IN YEAR ( NO ADDING) 40 weeks- drops at 2 fingers below the xiphoid IF: APRIL- DEC process due to lightening - MINUS 3 IN MONTH - ADD 7 IN DAY - ADD 1 IN YEAR Ex. JUNE 16, 2024 - CONVERT INTO NUMERICAL = 6 16 2024 - 3 +7 +1 3 23 2025 is the estimated date of labor. Ex. March 1, 2024 = 3 1 2024 +9 +7 ( as it is) 12 8 2024 is the estimated labor date. 2. Fetal growth ( Bartholomew’s Rule): Measures the height of the mother’s fundus - OVER SYMPHISIS PUBIS AT 12 WEEKS - AT UMBILICUS AT 20 WEEKS - AT THE XIPHOID PROCESS ( BELOW YOUR STERNUM) AT 36 WEEKS