Intro 30: Derivatives of endoderm and pharyngeal arches Flashcards
ENDODERM gives rise to…
EPITHELIAL lining of various body parts
WEEK 3, during GASTRULATION
and EARLY SOMITE DEVELOPMENT, what do we get of the FOREGUT, MIDGUT, HINDGUT
patterning of the ENDODERM into FOREGUT, MIDGUT, HINDGUT PROGENITOR DOMAINS
- future sits of foregut, midgut, hindgut are determined
as a result of EMBRYO FOLDING in WEEK 4..
FOREGUT and HINDGUT POCKETS FORM
- as the ENDODERMAL CUP is transformed into a GUT TUBE
what happens to the MIDGUT as foregut and hindgut pockets form during week 4?
MIDGUT remains in contact with the YOLK SAC until it DEGENERATES much LATER
ENDODERMAL SPROUTING results in the formation of what in the FOREGUT
UPPER SECTION of foregut:
primordial
- THYROID
- THYMUS
- LUNGS (lung bud)
LOWER SECTION of foregut:
primordial
- LIVER (liver bud)
- PANCREAS
when do we get development of the LIVER PRIMORDIUM / LIVER BUD
MIDDLE of 3RD WEEK
- appears as an outgrowth of
the ENDODERMAL EPITHELIUM at the distal end of the foregut
what plays a crucial role in INDUCTION of LIVER PROGENITOR CELLS (HEPATOBLASTS)
CARDIOGENIC MESODERM
what plays a crucial role in INDUCTION of LIVER PROGENITOR CELLS (HEPATOBLASTS)
CARDIOGENIC MESODERM
by providing extracellular signals
LIVER BUD CELLS differentiate into
PARENCHYMA (HEPATOCYTES)
haematopoietic cells, Kupffer cells and
connective tissue cells are derived from
MESODERM
Majority of the LIVER is derived from which germ layer
ENDODERM
but some from MESODERM (hepatic mesenchyme)
the PANCREAS is formed from 2 BUDS:
- DORSAL PANCREATIC BUD
- VENTRAL PANCREATIC BUD
the PANCREATIC BUDS (dorsal, ventral) originate from the ENDODERMAL LINING of the…
DUODENUM
which PANCREATIC BUD forms the UNCINATE PROCESS
VENTRAL PANCREATIC BUD
the VENTRAL pancreatic bud forms… (2)
- the UNCINATE PROCESS
- the VENTRAL PANCREAS / inferior part of the head of the pancreas
the rest of the pancreas is derived from the DORSAL PANCREATIC BUD
when do the pancreatic ISLETS OF LANGERHANS develop
3RD MONTH of embryonic development
when does INSULIN secretion begin
5TH MONTH
when does development of the RESPIRATORY DIVERTICULUM (LUNG BUD) take place
approx 4 WEEKS
- develops as an outgrowth from the
VENTRAL WALL of the foregut
Which parts of the RESPIRATORY SYSTEMare of ENDODERMAL origin
Epithelium of the internal lining of the larynx,
trachea,
bronchi
lungs
cartilaginous, muscular and connective tissue components of the trachea and lungs are derived from..
SPLANCHNIC MESODERM surrounding foregut
Lung bud EXPANDS CRANIALLY and 2 ridges appear and fuse:
TRACHEOESOPHAGEAL RIDGES
when TRACHEOESOPHAGEAL RIDGES FUSE what is formed
TRACHEOEPHAGEAL SEPTUM
TRACHEOEOPHAGEAL SEPTUM DIVIDES FOREGUT into :
Dorsal:
OESOPHAGUS
Ventral:
TRACHEA
& LUNG BUDS
4 stages of lung maturation:
- Pseudoglandular Period (6-16 weeks)
- Canalicular Period (16-26 weeks)
- Terminal Saccular Period (26 weeks to birth)
- Alveolar period (32 weeks to 8 years)
DERIVATIVES of the ENDODERM
- Digestive tract
- Epithelial lining of the respiratory tract
- Essential tissues of the thyroid, parathyroid, liver and pancreas
- Connective tissues of thymus and tonsils
- Epithelial lining of urinary bladder, urethra, tympanic membrane and auditory tube
Until the end of the 4th week,
the NEURAL TUBE is…
OPENED at the cranial and caudal NEUROPORES
BY DAY 24,
what appears as a result of EMBRYO GROWTH and FOLDING
PHARYNGEAL ARCHES appear
(arch-shaped FOLDS in the throat area)
due to rapid growth, the 3rd and 4th pharyngeal arches appear by day 28
How many PHARYNGEAL ARCHES are there in humans:
5
1,2,3,4 and 6 SIX
(no. 5 regresses almost immediately)
what is the name of PHARYNGEAL ARCH 1
MANDIBULAR ARCH
has 2 prominences:
- MAXILLARY 1
- MANDIBULAR 1
Which two PHARYNGEAL ARCHES FUSE
4 and 6
what is the name of PHARYNGEAL ARCH 2 and what does it do
HYOID ARCH
-forms most of HYOID BONE
What do PHARYNGEAL ARCHES 3 and 4 (fuses with 6) FORM
NECK STRUCTURES
Each PHARYNGEAL ARCH consists of
- CORE of MESENCHYME (MESODERM)
- ECTODERM (outside)
- ENDODERM (inside)
what does each PHARYNGEAL ARCH contain
- BLOOD VESSEL
- CARTILAGE
- MUSCULAR component
- NERVE
what innervate PHARYNGEAL ARCHES
cranial nerves
PA 1
aortic arch remnant?
which cranial nerve innervates it?
derivatives?
- Maxillary Artery
- Trigeminal Nerve
- muscles of mastication
- Meckel’s cartilage,maxilla, palatine bone, squamous temporal bone
PA 2
aortic arch remnant?
which cranial nerve innervates it?
derivatives?
- Stapedial and Hyoid Arteries
- Facial Nerve
- muscles of facial expression
- Reichert’s cartilage …lesser horn of hyoid
PA 3
aortic arch remnant?
which cranial nerve innervates it?
derivatives?
-common and internal Carotid Arteries
- Glossopharyngeal Nerve
- Stylopharyngeus
- Greater horn and inferior body of Hyoid Bone
PA 4
aortic arch remnant?
which cranial nerve innervates it?
derivatives?
-Arch of Aorta, right Subclavian artery
- Vagus nerve
- Pharyngeal and Palatal Muscles
- Thyroid Cartilage
PA 6
aortic arch remnant?
which cranial nerve innervates it?
derivatives?
- Ductus Arteriosus, Pulmonary arteries
- Vagus nerve
- most intrinsic muscles of Larynx
- Cricoid cartilage
what are also formed during PHARYNGEAL ARCH DEVELOPMENT
PHARYNGEAL CLEFTS AND POUCHES
pouches - structures in between arches
clefts- opposite pouches
THESE GIVE RISE TO IMPORTANT STRUCTURES
Abnormalities associated with
development of pharyngeal arches
EXAMPLES
TREACHER-COLLINS SYNDROME
(mandibulofacial dyostosis)
- Autosomal dominant
- 1/10,000 –1/50,000
- No ossification, no development of
MANDIBLE
- Mandibular and malar hypoplasia
- Abnormal external, middle and inner
ear (conductive hearing loss)
- Lower eyelid defects
PIERRE ROBIN SEQUENCE
- Likely autosomal dominant
- 1/4,000 –1/10,000 live births
- Triad of orofacial morphological
anomalies: micrognathia, retrognathia,
glossoptosis and a posterior median
velopalatal cleft (U-shaped)
DI-GEORGE SYNDROME
- Autosomal dominant
- 1/4,000 live births
- Caused by DELETION of small segment
of CHROMOSOME 22 –CATCH22
- Cardiac abnormality
- Abnormal facies
- Thymic aplasia (infections)
- Cleft palate
- Hypocalcemia/Hypoparathyroidism
At 23 DAYS (week 4)
- Neural folds have fused to form the
NEURAL TUBE (primordium of the spinal
cord in this region) - The neural tube is still OPENED at the
cranial and caudal ends and
communicates with the amniotic cavity
via cranial (rostral or anterior) and
caudal (posterior) neuropores - 10-somite embryo
At 23 DAYS (week 4)
- Neural folds have fused to form the
NEURAL TUBE (primordium of the spinal
cord in this region) - The neural tube is still OPENED at the
cranial and caudal ends and
communicates with the amniotic cavity
via cranial (rostral or anterior) and
caudal (posterior) neuropores - 10-somite embryo
At DAY 23 (week 4)
- Neural folds have fused to form the
NEURAL TUBE (primordium of the spinal
cord in this region) - The neural tube is still OPENED at the
cranial and caudal ends and
communicates with the amniotic cavity
via cranial (rostral or anterior) and
caudal (posterior) neuropores - 10-SOMITE embryo
at DAY 24 (week 4)
- The rostral / CRANIAL NEUROPORE is CLOSING, but the
CAUDAL NEUROPORE is still OPEN - The embryo is starting to CURVE because of FOLDING of the cranial and caudal ends
- 13-SOMITE embryo
at DAY 26 (week 4)
- The embryo is very CURVED with prominent tail-like CAUDAL EMINENCE
- 27-SOMITE embryo
- The LENS PLACODE is the primordium of the lens of the eye
- The ROSTAL NEUROPORE is CLOSED (caudal open)
- 3 PAIRS of PHARYNGEAL ARCHES are present
- The PRIMORDIAL HEART produces a large ventral prominence and PUMPS BLOOD
at DAY 28 (week 4)
- The primordial heart is large and
divided into a PRIMORDIAL ATRIUM and
VENTRICLE - Both rostral and caudal NEUROPORES
are CLOSED - The embryo has a characteristic C-SHAPED curvature (due to folding)
- UPPER and LOWER LIMB BUDS are
visible
-4 PAIRS of PHARYNGEAL ARCHES are
present
at WEEK 5 - day 32
- Rapid development of the BRAIN and
FACIAL PROMINENCES, face contacts the
heart prominences (really curved) - The MESONEPHRIC RIDGES indicate the SITE OF MESONEPHRIC KIDNEYS, an interim functional kidney
- The UPPER LIMB BUDS are PADDLE-SHAPED, whilst the LOWER LIMB BUDS
are FLIPPER-LIKE
WEEK 6 - day 42
- The DIGITAL RAYS (primordia of the
digits - fingers/toes) begin to develop - The AURICULAR HILLOCKS develop and
CONTRIBUTE to the formation of auricule
(EXTERNAL EAR) - RETINAL PIGMENT is visible (where eyes would be)
- The embryo shows SPONTANEOUS MOVEMENTS and RESPONSES TO TOUCH
WEEK 8 - day 56
- At the beginning of the eight week the
DIGITS of the hand and feet are separated,
but still webbed; by the END OF THE WEEK DIGITS have lengthened and SEPARATED - The SCALP VASCULAR PLEXUS appears
- COORDINATED LIMB MOVEMENTS occur for the first time
- PRIMARY OSSIFICATION begins in FEMUR
- At the end of the eight week the embryo
has VISUALLY DISTINCT HUMAN CHARACTERISTICS
when are both rostral and caudal NEUROPORES CLOSED
DAY 28 of week 4
when do we get MESONEPHRIC RIDGES, which mark the site of mesonephric kidneys
WEEK 5 - DAY 32
When is the embryo very CURVED with a CAUDIAL EMINENCE
DAY 26 of week 4
- starts curving at day 24
how many pairs of PHARYNGEAL ARCHES are present at DAY 26 (week4)
3 PAIRS
how many pairs of PHARYNGEAL ARCHES are present at DAY 28 (week4)
4 PAIRS
when is the PRIMORDIAL HEART present and PUMPING BLOOD
DAY 26 of week 4
when does the PRIMORDIAL HEART divide into ATRIUM and VENTRICLE
DAY 28 of week 4
When is the first COORDINATED LIMB MOVEMENT
WEEK 8 (day 56)
when does the embryo show SPONTANEOUS MOVEMENTS and RESPONSES to TOUCH
WEEK 6 (day 42)
when is the NEURAL TUBE formed (by fusion of neural folds)
DAY 23 of week 4
how many SOMITEs present at DAY 23 (week 4)
10 SOMITE EMBRYO
how many SOMITES present at DAY 24 (week 4)
13 SOMITE EMBRYO
how many SOMITES present at DAY 26 (week 4)
27 SOMITE EMBRYO
when does the RANIAL NEUROPORE close
DAY 26 (week 4)
starts closing at day 24
when does the CAUDAL NEUROPORE close
DAY 28 (week 4)
when do the DIGITAL RAYS begin to develop
WEEK 6 (day 42)
when do the DIGITS SEPARATE
END of WEEK 8
when is the RETINAL PIGMENT present
WEEK 6
when do we have rapid development of the BRAIN and FACIAL PROMINENCES
WEEK 5 (day 32)
When do the UPPER and LOWER LIMB BUDS appear
DAY 28 (week 4)
upper is paddle-shaped and lower is flipper-like at week 5
when does the SCALP VASCULAR PLEXUS appear
WEEK 8 (day 56)
when does the AURICULAR HILLOCKS develop (contributes to formation of external ear - auricle)
WEEK 6 (day 42)
when does PRIMARY OSSIFICATION begin in FEMUR
WEEK 8
when do we have VISUALLY DISTINCT HUMAN CHARACTERISTICS
END OF WEEK 8
when does the embryo have a C-SHAPED CURVATURE due to folding
DAY 28 (week 4)
When do we get the LENS PLACODE (primordium of lens)
DAY 26 (week 4)