Langman Medical Embryology Made Easy
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Transcript of Langman Medical Embryology Made Easy
OOGENESIS
BEFORE BIRTH…
↓
Primordial Germ Cells (developed in Epiblast; 2nd
Week)
↓
MIGRATES TO Yolk Sac
↓
MIGRATES TO Developing Gonads (End of 5th
Week)
↓
Oogonia (2N)
↓
DIVIDES (by mitosis) TO FORM Primary Oocyte
↓
Mitosis results to INCREASE NO. OF OOGONIA AND
PRIMARY OOCYTE
↓
TOTAL NO. GERM CELLS REACHES MAXIMUM (7
MILLION)
↓
SO, CELL DEATH BEGINS (OOGONIA AND PRIMARY OOCYTE
BECOMES ATRETIC)
↓
Surviving Primary Oocytes undergo MEIOSIS I PROPHASE I
DIPLOTINE STAGE (1st arrest)
↓
BIRTH…
↓
600,000-800,000 Primary Oocyte
↓
↓
CHILDHOOD…
↓
Primary oocyte becomes Atretic
↓
BEGINNING PUBERTY…
↓
40,000 Primary Oocyte, fewer than 500 will be ovulated
↓
↓
PUBERTY…
↓
↓
↓
↓
↓
MEIOSIS I CONTINUES AND FINALLY COMPLETED
↓
Secondary Oocyte + 1st
Polar Body
↓
METAPHASE II OF MEIOSIS II (2ND
Arrest)
↓
Fertilization””/ No Fertilization
↓
MEIOSIS II CONTINUES AND FINALLY COMPLETED/
secondary oocyte degenerates
FOLLICLE MATURATION
BEFORE BIRTH…
↓
↓
↓
Primary Oocyte surrounded by thin layer of follicular cells
↓
Primordial Follicle
↓
↓
↓
↓
↓
BIRTH…
↓
(FSH) Surrounding follicular cells change from flat to cuboidal and
gradually become stratified epithelium forming GRANULOSA CELLS.
↓
GRANULOSA CELLS secrete glycoproteins forming ZONA
PELLUCIDA
↓
Primary Follicle
↓
Cells of THECA FOLLICULA organize into THECA INTERNA and
THECA EXTERNA, formation of Antrum
↓
PUBERTY…
↓
Secondary Follicle (LH AND FSH)^^^^
↓
As Antrum enlarges, granulosa remain intact, thus forming CUMULUC
OOPHORUS
↓
Graafian Follicle (surge in LH)
OVARIAN CYCLE
HYPOTHALAMUS
↓
GnRH
↓
GONADOTROPINS
↓
FSH^^
↓
Stimulates growth and maturation of GRANULOSA CELLS
↓
GC Together with THECA INTERNA
↓
Produce ESTROGEN^^
↓
Estrogen stimulates Anterior Pituitary Gland
↓
Produce LH^^
↓
Stimulates FOLLICULAR CELLS
↓
Produce PROGESTERONE
^^FSH
↓
Nourishes the follicular cells of PRIMORDIAL FOLLICLE,
saving the 25-20 Primary follicle from dying and become
atretic
^^ESTROGEN
↓
Uterine Endometrium enter FOLLICULAR/PROLIFERATIVE
PHASE
/ Thinning of cervix mucus to allow passage of sperm
^^LH
↓
Maturation promoting factor / Follicular Rupture and
Ovulation
↓
Maturation of secondary follicle and completion of Meiosis
I
^^^^ OVULATION (Follicular/ Proliferative Phase)
ESTROGEN
↓
Maturation of Secondary Follicle
↓
LH SURGE
↓
Secondary follicle forms into Graafian follicle
↑ Collagenase activity/ ↑Prostaglandins level
↓
Digestion of Collage fibers surrounding the follicles/ Local
muscular contraction in Ovarian walls
↓
Uterine Tube contract Rhythmically
↓
The PRIMARY OOCYTE is extruded from the ovary
together with cumulus oophorus
↓
Fimbrae sweeps over the surface of ovary
↓
SECONDARY OOCYTE is propelled by peristaltic
movement or contraction of Uterine Tube
↓
SECONDARY OOCYTE on uterine tube
↓
Cumulus Oophorus rearrange around the zona pellucida
↓
Forming CORONA RADIATA**
“”FERTILIZATION
Sperm
↓
Passes the Vagina
↓
Passes the Cervix
↓
Muscular contraction of uterus and uterine tube
Uterine tube (2 to 7 hours)
↓
Isthmus of Uterine tube
↓
(Sperm becomes less motile and cease their migration)
↓
CUMULUS OOPHORUS produce chemo-attractants
stimulating motility of sperm
↓
Sperm in AMPULLA
↓
CAPACITATION
(conditioning of the female reproductive tract; involves
epithelial interaction between sperm and mucosal surface
of the tube)
↓
Glycoprotein coat and seminal plasma proteins are
removed from the acrosome of spermatozoa
↓
SPERM passes through
CORONA RADIATA
↓
Acrosome reaction
↓
Sperm passes through ZONA PELLUCIDA
(Alters the property of ZONA Pellucida, preventing other
sperm from entering)
↓
FUSION OF SPERM AND EGG CELL MEMBRANES
**CORPUS LUTEUM (SECRETORY PHASE)
If oocyte is not fertilized…
Remains of the Ruptured Follicle (GRANULOSA CELLS +
THECA INTERNA)
↓
Vascularized by surrounding vessels
↓
Develops into LUTEAN CELLS
↓
CORPUS LUTEUM
↓
CORPUS LUTEUM reaches maximum development
approx. 9 days after ovulation
↓
CORPUS LUTEUM shrinks and produce PROGESTERONE
↓
Becomes CORPUS ALBICANS
↓
Venules and sinusoidal space become packed with blood
cells/ extensive diapedesis in blood tissues
↓
Shedding of Endometrium (Menstruation)
If oocyte is fertilized…
Remains of the Ruptured Follicle (GRANULOSA CELLS +
THECA INTERNA)
↓
Vascularized by surrounding vessels
↓
Develops into LUTEAN CELLS
↓
CORPUS LUTEUM
↓
CORPUS LUTEUM does not degenerate
(Under influence of HCG)
↓
Develops into CORPUS LUTEUM of PREGNANCY
↓
Produce PROGESTERONE (until end 4th
month that the
uterus is ready for implantation)
↓
IMPLANTATION
↓
Uterine glands and arteries become coiled and tissues
become succulent
CLEAVAGE
Uterine Tube…
↓
2 Cell Stage
↓
4 Cell Stage (formation of blastomeres)
↓
COMPACTION (Blastomeres maximize their contact with
each other; segregates inner cell mass from outer cell
mass)
↓
8 Cell Stage
↓
16 Cell Stage – Morula
↓
Morula enters Uterine Cavity…
↓
Fluid begins to penetrate zona pellucida
↓
Forming BLASTOCOELE
↓
Formation of inner cell mass and outer cell mass
↓
BLASTOCYST
↓
Zona pellucida disappears
↓
IMPLANTATION (Trophoblastic cells penetrate epithelial
cells of Uterine Mucosa)
SPERMATOGENESIS
PRIMORDIAL GERM CELLS is at Sex cords At Birth
↓
Before Puberty… Sex cord obtain lumen and form Seminiferous tubules
↓
PG develops into SPERMATOGONIAL STEM CELLS
↓
Differentiate to SPERMATOGONIA TYPE A
↓
Divides by mitosis to form SPERMATOGONIA TYPE B
↓
Divides by mitosis to form PRIMARY SPERMATOCYTE
↓
Meiosis I prolonged
↓
Puberty
↓
Meiosis I completed
↓
Forms SECONDARY SPERMATOCYTE
↓
Meiosis 2 completed
↓
Forms SPERMATIDS
↓
Spermiogenesis (1. Formation of acrosome, 2. Condensation of nucleus, 3. Formation of neck, midpiece and tail and 4. Shedding of cytoplasm)
↓
Mature Spermatozoa
↓
Lumen of Seminiferous Tubules
↓
Epididymis
2nd
Week of Development (FORMATION OF BILAMINAR DISC)
Day 8… Day 9…
Day 11 and 12…
Day 13…
Blastocyst attaches its outer cell mass in the epithelium of Endometrial Stroma Blastocyst forms: o Trophoblast (Outer Cell Mass)
Cytotrophoblast
(mononucleated)
Syncytiotrophoblast
(multinucleated)
o Embryoblast (Inner Cell Mass)
Hypoblast
(Cuboidal cells) Epiblast
(Columnar cells)
Amnioblast
o Blastocyst cavity
Blastocyst is partially embedded in the endometrial stroma
Penetration defect is closed by FIBRIN COAGULUM
Appearance of LACUNAE in
syncytiotrophoblast
Blastocyst cavity becomes PRIMITIVE YOLK SAC
Hypoblast forms the EXOCOELOMIC MEMBRANE
(Heuser’s Membrane) – lining of primitive yolk sac
Blastocyst is completely embedded in endometrial stroma
Surface epithelium almost entirely covers the original defect in the uterine wall
Syncytiotrophoblast penetrate deeper into the stroma and erodes endothelial lining → Maternal blood enters lacunae → Establishment of UTEROPLACENTAL CIRCULATION
Exocoelomic Membrane becomes EXTRAEMBRYONIC MESODERM
o SOMATOPLEUR (Somatic
Mesoderm) o SPLANCHNOPLEUR (Visceral
Mesoderm)
Primitive Yolk Sac becomes the SECONDARY/ DEFINITE YOLK SAC
Extraembryonic coelom expands to form CHORIONIC CAVITY
3rd
WEEK (GASTRULATION & NEURULATION)
Day 14 Day 16 - 18
Formation of PRIMITIVE STREAK
Migration of Epiblast cells o Towards the hypoblast – ENDODERM o Epiblast and newly created endoderm – MESODERM o Remains in the epiblast – ECTODERM
*These cells spread laterally and cranially
Formation of NOTOCHORD (Basis of axial skeleton)
Elongation o Cranial end (from prechordal plate) o Caudal end are added (in primitive pit) o Primitive pit forms indentation in the epiblast – neurenteric canal
temporarily connects the amniotic and yolk sac cavities o CLOACAL MEMBRANE is formed at the caudal end
Mesoderm differentiates into: o PARAXIAL MESODERM (midline) o LATERAL PLATE MESODERM (lateral)
Mesoderm covering the Amnion – Somatic or Parietal Mesoderm
Mesoderm covering the Yolk Sac – Splanchnic or Visceral Mesoderm
Both mesoderm forms the INTRAEMBRYONIC CAVITY o INTERMEDIATE MESODERM (connects paraxial and lateral plate mesoderm)
NEURULATION
Day 19 Day 20 Day 23 Day 25 Day 28
Formation of NEURAL
PLATE
Neuroectoderm becomes elevated forming the NEURAL FOLDS
Neural folds fuse cranially and caudally forming the NEURAL TUBE
Closure of the ANTERIOR NEUROPORE (18 –
20 somite stage)
Closure of POSTERIOR NEUROPORE (25
somite stage)
4th
WEEK (ORGANOGENESIS)
ECTODERM
NEURAL TUBE NEURAL CREST CELLS
o Cranial region – forms the BRAIN VESICLES Prosencephalon (FOREBRAIN)
o Telencephalon – CEREBRUM o Diencephalon – OPTIC CUP, THALAMUS, HYPOTHALAMUS and
EPIPHYSIS
Mesencephalon (MIDBRAIN)
RHOMBOCEPHALON (HINDBRAIN) o Metencephalon – CEREBELLUM, PONS o Myelencephalon – MEDULLA OBLONGATA
o Caudal region – forms the SPINAL CHORD
They migrate into :
o CRANIAL NEURAL FOLDS to form: CRANIOFACIAL SKELETON NEURONS FOR CRANIAL GANGLIA GLIAL CELLS
o Mesoderm in 2 pathways: DORSAL PATHWAY
MELONOCYTE
VENTRAL PATHWAYS
SENSORY GANGLIA
ENTERIC NEURONS
SCHWANN CELLS
ADRENAL MEDULLA CELLS
MESODERM
PARAXIAL MESODERM LATERAL PLATE MESODERM INTERMEDIATE MESODERM
SOMITES
SOMITOMERES Somatic mesoderm Splanchnic Mesoderm
Metanephric Mesodern
Ureteric Bud
SCLEROTOME DERMATOME MYOTOME
o Ventromedial forms
the cartilage, tendons and bones
o Vertebrae Primary Curves
• THORACIC CURVE • SACRAL CURVE
Secondary Curves • CERVICAL CURVE
(develops when a child learns to hold up his head)
•LUMBAR CURVE (develops when a child learns to walk)
o Intervertebral disc
o Together with Lateral Plate mesoderm forms the COSTAL CARTILAGE
o BONY PART OF THE
RIBS
o Remains in the middle –forms the dermis of back
o Dorsomedial & Ventrolateral –forms the segmental muscles
o Cranially (in
association with neural plate) – forms the NEUROMERES
and then into MESENCHYME OF THE HEAD
o Caudally to form the
SOMITES which will form the AXIAL SKELETON
w/ ectoderm – dermis of skin in body wall, connective tissue of limbs
w/ sclerotome and myotome – costal cartilage, limb muscles and most body wall muscles
surround in intraembryonic cavity – mesothelial and serous membranes
MANUBRIUM, STERNEBRAE XIPHOID PROCESS
Together with
neural crest cells form SMOOTH MUSLES
w/ embryonic endoderm – wall of Gut Tube
Hemangioblast →blood islands → blood cells
o Stroma of glands
o Visceral muscles,
connective tissue and Peritoneal components of the gut
o Bowman’s
capsule
o Proximal Convulated Tubule
o Loop of Henle
o Distal Convulated Tubule
o Ureter
o Renal
Pelvis
o Major
Calyx
o Minor Calyx
DERMOMYOTOME
Ventrolateral lip o INFRAHYOID, ABDOMINAL
WALL, LIMB MUSCLES
Dorsolateral lip o Muscles of the back,
shoulder girdle and intercostal muscles
ENDODERM
FOREGUT MIDGUT - HINDGUT
Dorsal portion of the Respiratory Diverticulum forms the ESOPHAGUS
Fusiform dilation of the foregut forms the
STOMACH
The terminal part of the foregut and the cephalic part of the midgut forms the DUODENUM
Outgrowth of the endodermal epithelium at the
distal end of the foregut forms the LIVER
Small ventral outgrowth formed by the bile duct forms the GALLBLADDER
o Formed from the two buds of the endodermal
lining of duodenum is the PANCREAS
o Epithelial lining of digestive tract o Hepatocytes, endocrine and exocrine glands
of pancreas
Cephalic limb of the primary intestinal loops develop into DISTAL PART OF DUODENUM, JEJUNUM AND PART OF ILEUM
Caudal limb of the primary intestinal loops
becomes the LOWER PORTION OF ILEUM, CECUM, APPENDIXASCENDING COLON AND PROXIMAL 2/3 OF TRANSVERSE COLON
*formed from rapid elongation of the gut and its mesentery
o
DISTAL 1/3 OF TRANSVERSE COLON
DESCENDING COLON
SIGMOID
RECTUM
UPPER PART OF ANAL CANAL (derived from
endoderm of hindgut and ectoderm of proctodeum)
INTERNAL LINING OF BLADDER AND
URETHRA
*degeneration of cloacal membrane establish continuity between upper and lower part of anal canal
Orientation of BODY PARTS
LIMBS STOMACH DUODENUM
o FORELIMBS (1
st)
Rotates 90 degree laterally
Extensor muscles lie laterally and posteriorly, thumbs on lateral side
o HINDLIMBS (2nd
) Rotates 90 degree medially
Extensor muscles at the anterior, toes at the medial side
SEGMENTATION OF THE LIMBS First circular constriction separates distal segment
(foot/hand) from proximal segment (legs) Second circular constriction divides proximal
portion into two segments (the thigh and the legs)
90 DEGREE CLOCKWISE ROTATION AROUND THE LONGITUDINAL AXIS
o Left side of the stomach face anteriorly o Right side of the stomach face posteriorly o Greater Curvature of the Stomach (formed
because posterior wall of stomach grows faster than anterior wall)
ROTATION ON THE ANTEROPOSTERIOR AXIS
o Caudal or pyloric part moves right, upward o Cephalic or cardiac portion moves left
downward
ROTATION OF STOMACH ON ANTEROPOSTERIOR AXIS
o Duodenum forms a C shaped loop and rotates to the right
o Swings duodenum from midline to right of abdominal cavity
o FINGERS and TOES Distal portion thickens and forms APICAL ECTODERMAL RIDGE (AER)
AER inducts the adjacent mesenchyme causing it to remain undifferentiated, rapidly, proliferating cells called PROGRESSIVE ZONE Cell death in AER separate ridges into 5 parts o FEET/HANDS
Terminal portion becomes flattened to form HAND AND FOOT PLATES
PHARYNGEAL ARCH
1ST
PHARYNGEAL ARCH 2ND
PHARYNGEAL ARCH
(Hyoid arch)
3RD
PHARYNGEAL ARCH 4TH
AND 6TH
PHARYNGEAL ARCH
o Maxillary Process (Dorsal)
PREMAXILLA, MAXILLA, ZYGOMATIC BONE, part of TEMPORAL BONE
o Mandibular Process (Ventral) INCUS, MALLEUS
o TRIGEMINAL NERVE
o STAPES, STYLOID PROCESS,
TEMPORAL BONE, STYLOHYOID LIGAMENT, LESSER HORN and UPPER PART OF THE BODY OF HYOID BONE
o FACIAL NERVE
o LOWER PART OF THE BODY
OF HYOID BONE, GREATER HORN OF HYOID BONE
o GLOSSOPHARYNGEAL NERVE
o THYROID, CRICOID,
ARYTENOID, CORNICULATE CUNEIFORM CARTILAGE OF LARYNX
o SUPERIOR LARYNGEAL BRANCH OF VAGUS NERVE (4
TH Arch)
o RECURRENT LARYNGEAL BRANCH OF VAGUS NERVE (6
TH Arch)
1ST
PHARYNGEAL CLEFTS o EXTERNAL AUDITORY MEATUS
PAHRYANGEAL POUCH
1ST
PHARYNGEAL POUCH 2ND
PHARYNGEAL POUCH 3RD
PHARYNGEAL POUCH 4TH
PHARYNGEAL POUCH
o TYMPANIC MEMBRANE
(Distal) o EUSTACHIAN TUBE
(Proximal)
Palatine Tonsils
o INFERIOR PARATHYROID
GLAND (Dorsal) o THYMUS (Ventral)
o SUPERIOR PARATHYROID GLAND (Dorsal)
o ULTIMOBRANCHIAL BODY (Ventral)
Parafollicular Cells of Thyroid Gland
Calcitonin
TONGUE
MESODERM OF 1ST
PHARYNGEAL ARCH
MESODERM OF 2ND
, 3RD
AND 4
TH PHARYNGEAL ARCH
Posterior Part of the 4TH
Arch
LATERAL LINGUAL SWELLING
1ST
MEDIAL SWELLING
2ND
MEDIAN SWELLING 3rd
MEDIAN SWELLING
Anterior 2/3 of TONGUE
Anterior 1/3 of TONGUE
Posterior Root of TONGUE EPIGLOTTIS
MAXILLARY PROMINENCE FRONTONASAL PROMINENCE
MANDIBULAR PROMINENCE
Merge with 2 MEDIAL NASAL PROMINENCE
Merge with the INTERMAXILLARY SEGMENT Merge across the midline
UPPER LIP
UPPER JAW COMPONENT
LABIAL COMPONENT
PALATAL COMPONENT
LATERAL NASAL PROMINENCE
MEDIAL NASAL PROMINENCE
LOWER LIP
4 INCICOR TEETH
PHILTRUM OF UPPER LIP
TRIANGULAR PRIMARY PALATE
SIDE OF NOSE AND CHEEKS
CREST AND TIP OF NOSE
2nd
MONTH TO BIRTH
Month Development
2nd
Month (5
th week – 8
th week)
LIMBS AND HEAD
INCREASE IN HEAD SIZE FORELIMBS APPEAR as paddle shaped buds HINDLIMBS appear later
3RD
Month ( 9th
– 12th
week) FULL DEVELOPMENT OF ORGANS
Slowdown in the growth of the head compared to the rest of the body FACE becomes more HUMAN –LIKE EYES from lateral position moves to the ventral portion of the head Ears comes to lie at their definite position in the head Limbs reach their relative length Primary ossification are present in long bones and skull External genitalia develop to such degree that the sex of the fetus can be determined Large swelling (Herniation) has withdrawn into the abdominal cavity
4th
( 13th
– 16th
weeks) LENGTH
Fetus lengthens rapidly Weight increase a little Fetus is covered with fine hair (lanugo), eyebrows are visible
5th
Month (17th
– 20th
weeks) WEIGHT
Movements of fetus can be felt by the mother Weight increase rapidly Fetus swallows its own amniotic fluid (400 mL a day) – FETAL urine is added daily to the amnion
6th
Month (21ST
24TH
weeks) RED SKIN
Skin is reddish and wrinkled because lack of underlying connective tissue Fetus born in this month cannot survive since Respiratory and Nervous System has not yet sufficiently differentiated
7 Months (25th
- 28th
weeks) WHITE SKIN
Fetus obtains well rounded contours as a result of fat deposition The skin is covered with whitish fatty substance (Vernix caseosa) composed of secretory products of sebaceous glands
9th
Month ( 33th - 36 weeks) FETUS READY FOR DELIVERY
Skull has the largest circumference of all parts of the body
CHANGES IN THE TROPHOBLAST/ PLACENTA
2nd
MONTH 4TH
MONTH 5TH
MONTH
Cytotrophoblastic cells invades
(ENDOVASCULAR INVASION) the terminal ends of SPIRAL ARTERIES
This transforms SPIRAL ARTERIES from small diameter, high resistance vessels to large diameter, low resistance vessels
Spiral arteries release blood into the INTERVILLOUS SPACE – derived from lacunae of Syncytiotrophoblast; filled with maternal blood
Cytotrophoblastic cells and connective tissue cells
disappears due to increase in diameter of villi The SYNCYTIUM and ENDOTHELIAL WALL OF
BLOOD VESSELS are the only layers that separate maternal and fetal circulation
Villi covers the surface of the CHORION Villi grow and expand to form CHORION
FRONDOSUM
Villi on abembryonic region degenerate forming CHORION LEVAE
CHRORION LEVAE comes in contact with DECIDUA PARIETALIS on the opposite side of the uterus and fuse, obliterating the uterine lumen
Amnion expands, and come in contact with Chorion, obliterating the CHORIONIC CAVITY; yolk sac shrinks and gradually obliterated
Placenta produce: o PROGESTERONE to maintain pregnancy
(synthesized in SYNCYTIAL TROPHOBLAST) o ESTROGEN just before end of pregnancy to
promote uterine development and growth of mammary glands
o hCG to maintain Corpus luteum o Placental lactogen which gives fetus priority on
maternal blood glucose and makes mother diabetogenic; promotes breast development for
PLACENTA ENLARGES with growth of the fetus
and expansion of Uterus not due to further penetration into maternal tissues but due to arborisation of existing villi
PARTURITION
EFFACEMENT
DELIVERY OF THE FETUS
DELIVERY OF THE PLACENTAL MEMBRANES
o Uterine contracts, amniotic sac s forced against the cervical canal like a wedge
o If memebrane is ruptured, pressure will be exerted by the presenting part of the fetus, usually the HEAD
o Uterus contracts o Increased intraabdominal pressurefrom
contraction of Abdominal Muscles
o Uterine contractions o Abdominal muscle contraction
PLACENTA
Placenta is composed of:
CHORION FRONDOSUM (Fetal Component) – derived from TROPHOBLAST
and EXTRAEMBRYONIC MESODERM
o Bordered by CHORIONIC PLATE
DECIDUA BASALIS (Maternal Component) – derived from UTERINE
ENDOMETRIUM
o Bordered by DECIDUAL PLATE
o Contains compartments called COTYLEDONS – maintain its contact with
INTERVILLOUS SPACE through DECIDUAL SEPTA
Function:
Exchange of gases (simple diffusion)
Exchange of nutrients
Transmission of Maternal Antibodies
Hormone Production (hCG , progesterone, estrogen and placental lactogen)
Full Term Placenta:
Discoid
15 to 25 cm in diameter
3 cm thick
Weighs 500 to 600 grams
Form from uterine wall at birth
Expelled 30 minutes after birth
On MATERNAL SIDE:
Contains 15 TO 20 cotyledons covered by decidua basalis
On FETAL SIDE:
PLACENTA is covered by CHORIONIC PLATE
CHORIONIC VESSELS converge toward the umbilical cord
CHORION is covered by AMNINON
4 Layers of Placental Membrane:
Endothelial lining of Fetal Vessels
Connective Tissue on Villous Core
Cytotrophoblastic layer
Syncytium
The Amniotic Fluid
Derived from maternal blood
Produced by amniotic cells
Clear, watery fluid replaced every 3 hours
Normal amount:
o 10 weeks – 30 mL
o 20 weeks – 450 mL
o 37 weeks – 800 – 1000 mL
Function:
Absorbs jolt
Prevents adherence of embryo to the amnion
Allow fetal movements
The Umbilical Cord
Distally, contains :
o Yolk Stalk
o Umbilical vessels
Proximally contains:
o Intestinal loop
o Remnant of Allantois
Resource: Langman’s MedicalEmbryology, 11th
Edition
Compiled and condensed by: Ma. Theresa Monje
August 21, 2012