Transcript Embryology File

Embryology
Pedro Amarante Andrade, PhD
LCSC06
BIOSCIENCES
FOR SPEECH AND LANGUAGE THERAPY
LCSC06 | Biosciences for SLT
INTRODUCTION TO
EMBRYOLOGY
• Basic concepts and principles
• How the embryo develops from fertilisation to
implantation – brief overview (for your information)
• Influences on the growth and development of the
embryo; critical period concept
• Important stages in development: gastrulation,
neurulation, development of the nervous system
• The neural crest cells – and their fate
• Embryonic development of the head and neck
structures
LCSC06 | Biosciences for SLT
DIRECTED STUDY ELEMENTS
• Basic genetics
• To understand how the pharyngeal arches
develop and contribute to the development
of the structures of the face, neck and palate
• Relate this development to the structures of
the head and neck you are currently studying
LCSC06 | Biosciences for SLT
EVERYBODIE’s JOURNEY
https://en.wikipedia.org/wiki/File:HumanNew
born.JPG
https://en.wikipedia.org/wiki/File:Human_e
mbryo_2.jpg
https://insideoutsrikar.f
iles.wordpress.com/20
11/12/zygote.jpg
LCSC06 | Biosciences for SLT
WHY STUDY
EMBRYOLOGY?
LCSC06 | Biosciences for SLT
PREGNANCY: MEASURED IN
TRIMESTERS
http://americanpregnancy.org/week-by-week/7-weekspregnant/
LCSC06 | Biosciences for SLT
REAL STAGES
• Prenatal development:
3 stages of unequal length
• Germinal stage: days 1 to 14
(i.e. from conception to implantation)
• Embryonic stage: begins at implantation
approximately 2 weeks after conception and
continues through weeks 3 to 8
(the period oforganogenesis )
LCSC06 | Biosciences for SLT
REAL STAGES
• The Foetal Stage: from 9th week to the birth
(40 weeks from last period, or 38 weeks from
fertilisation)
• Organs grow and continue differentiation
• Increase in weight
LCSC06 | Biosciences for SLT
CHALLENGES IN STUDYING
EMBRYOLOGY
•
•
•
•
Complexity
Personal experience
Attitudes and beliefs
Terminology
LCSC06 | Biosciences for SLT
PRE-EMBRYONIC PERIOD
Germinal Stage
• The first 14 days
• Cells can still repair themselves
• If damaged  either repairs or dies
(spontaneous miscarriage)
LCSC06 | Biosciences for SLT
CRITICAL PERIOD
http://image.slidesharecdn.com/2015-150325050652-conversiongate01/95/human-embryology-2-638.jpg?cb=1427260053
LCSC06 | Biosciences for SLT
WHAT CAN AFFECT PRENATAL
DEVELOPMENT?
LCSC06 | Biosciences for SLT
WHAT CAN AFFECT PRENATAL
DEVELOPMENT?
•
•
•
•
Chromosomal and genetic factors
Teratogens: maternal disease, drugs
Mutagens: radiation
Other maternal influences on development:
– Diet, age, chronic illness, environmental
hazards and maternal emotions
LCSC06 | Biosciences for SLT
CHROMOSOMAL &
GENETIC FACTORS
90% of abnormal embryos are
spontaneously aborted
Only 1% of live new-borns have a genetic
abnormality
LCSC06 | Biosciences for SLT
CHROMOSOMAL ABNORMALITIES
• 23 pairs of chromosomes
• 50+ different chromosomal abnormalities
– Too many chromosomes
– Too few chromosomes
• Vast majority of chromosomal abnormalities
are lethal (spontaneous abortion)
LCSC06 | Biosciences for SLT
CHROMOSOMAL ABNORMALITIES
• Three copies of
chromosome 21
• 1 /600 birth
• Learning disability
(IQ averages 50)
• May have congenital eye,
ear, heart defect
• Distinctive physical
features: protruding
http://year9diseases.wikispaces.com/Dow
tongue, short
limbs,
n's+Syndrome
slightly flattened nose…
Down’s Syndrome
http://ehumanbiofield.wikispaces.com/JH+Downsydrome
LCSC06 | Biosciences for SLT
ANGELMAN’S SYNDROME AND
PRADER-WILLI SYNDROME
• Genetic defect on chromosome 15
– Angelman’s syndrome (maternal case)
– Prader-Willi syndrome (paternal case)
LCSC06 | Biosciences for SLT
KLINEFELTER’S SYNDROME
• Sex chromosomes:
XXY (boys)
• 1/500 births
• Poor coordination
• May have mild
learning difficulties
http://genmolecular.com/alteraciones-cromosomicas/
LCSC06 | Biosciences for SLT
TURNER’S SYNDROME
• Only affect girls
• Occur randomly
• 23rd X missing
https://en.wikipedia.org/wiki/Turner_syndrome
LCSC06 | Biosciences for SLT
GENETIC DISORDERS
• Through dominant or recessive genes (E.g. Cystic
fibrosis)
• Phenylketonuria (PKU)
– Lack of enzyme to digest food containing amino
acid phenylalanine (e.g.milk)
– Phenylpyruvic acid accumulates in the body and
attacks the developing nervous system
– Hyperactivity; learning difficulties
– Test routinely given at birth
– Treatment: diet
LCSC06 | Biosciences for SLT
MUTAGENS
• Caused by physical or chemical agents (e.g.
ionising radiation)
• Act on the DNA in cells, especially during cell
division
• Alters the genes
• Mutation can be passed on, if it occurs in the
gametes
LCSC06 | Biosciences for SLT
TERATOGENS
• Any disease, drug or other environmental
agent that can harm the developing embryo
or foetus
• The effect is worse on a body part when
that structure is forming or growing rapidly
• Critical period: Period when a body part is
most sensitive to teratogenic agents
LCSC06 | Biosciences for SLT
MATERNAL DISEASE
Rubella
– Most dangerous in first trimester
– Blindness, deafness, cardiac
abnormalities, mental retardation
Syphilis
– Most harmful in middle or later stages
– Miscarriage, serious eye, ear, bone, brain
damage
LCSC06 | Biosciences for SLT
TOXOPLASMOSIS
• ¼ adults have this mild disease – similar
to common cold
• Parasite (cat)
• Powerful teratogen
• Serious eye or brain damage, induce
spontaneous abortion
LCSC06 | Biosciences for SLT
DRUGS
Thalidomide
– In 60s
– Drug against sickness
given to pregnant women
in first trimester
– Violent teratogen
– Badly deformed eyes,
ears, nose, even missing
limbs
http://talubrinandoescritoschapadadoarapari.blogspot.c
o.uk/2012/09/a-minha-solidariedade-as-vitimas-da.html
LCSC06 | Biosciences for SLT
DRUGS
Smoking
• Low birth weight (less than 2.5 kg)
• Nicotine constricts blood vessels
 Reduces blood flow to placenta
LCSC06 | Biosciences for SLT
DRUGS
Alcohol:
• Foetal alcohol syndrome (FAS):
• Microcephaly
• Malformation of heart, limbs,
joints, face
• Smaller
• Lower IQ - More likely to have
learning difficulties (IQ < 85)
http://disindevt3.wikispaces.com/Foetal+Alcoh
ol+Syndrome
• Even low drinking, social drinking
LCSC06 | Biosciences for SLT
DRUGS
Mercury Poisoning
• Minamate disease
W Eugene Smith, 1972
LCSC06 | Biosciences for SLT
EMBRYOLOGICAL DEVELOPMENT
LCSC06 | Biosciences for SLT
ITERATIVE PROCESSES IN
EMBRYOLOGICAL DEVELOPMENT
•
•
•
•
•
•
Cell division (proliferation)
Cell adhesion
Separation of cell sheets to form cavities
Cell migration
Cell differentiation
Cell induction
LCSC06 | Biosciences for SLT
TIMING IS EVERYTHING
• Cell proliferation : embryo/organ system
vulnerable to genetic or environmental factors
• Cell migration: cells move into position; can be
affected by matrix through which they travel
• Cell differentiation: cells assume their ultimate
form or phenotype – less vulnerable to insult
LCSC06 | Biosciences for SLT
APOPTOSIS
http://eorif.com/syndactyly-7551
LCSC06 | Biosciences for SLT
EMBRYONIC DEVELOPMENT
• Weeks 1 and 2:
–Fertilisation
–Implantation
–Formation of the placenta
and the early embryo
http://www.wisegeek.com/what-is-thefertilization-process.htm
LCSC06 | Biosciences for SLT
FERTILISATION TO IMPLANTATION
http://humanphysiology2011.wikispaces.com/15.+Reproductive+Physiology
LCSC06 | Biosciences for SLT
DAY 1
DAY 2
2 cells; Genes ‘switch on’
8 to 16 cell stage
(morula)
LCSC06 | Biosciences for SLT
https://en.wikipedia.org/wiki/File:Embryo,_8_cells.jpg
DAY 3
DEVELOPMENT OF THE
BLASTOCYST
http://www.conceive.ca/fertility-treatments/in-vitro-fertilization-ivf
LCSC06 | Biosciences for SLT
THREE SOURCES OF EMBRYONIC
STEM CELLS
http://www.intechopen.com/books/pluripotent-stem-cells/de-differentiation-ofsomatic-cells-to-a-pluripotent-state
LCSC06 | Biosciences for SLT
DAY 14
https://quizlet.com/7189248/bilaminar-and-trilaminar-flash-cards/
LCSC06 | Biosciences for SLT
"It is not birth, marriage, or death, but
gastrulation, which is truly the most
important time in your life."
Lewis Wolpert (1986)
LCSC06 | Biosciences for SLT
GASTRULATION
A PROCESS THAT LASTS 2 WEEKS
• Gastrulation:
At this point, I suggest you do a Google
search of gastrulation images, as the best
ones are unfortunately subject to copyright
LCSC06 | Biosciences for SLT
THE FATE OF THE 3 GERM LAYERS
• Ectoderm: CNS, PNS, epidermis, hair, nails,
sensory epithelium (nose, ear, eye)
• Mesoderm: part of skull, muscles, vertebrae,
urogenital system, serous membranes, body
wall, limbs
• Endoderm: gut tube and its derivatives;
glands, lungs, liver, gall bladder, pancreas
LCSC06 | Biosciences for SLT
BIRTH DEFECTS ORIGINATING
DURING GASTRULATION
• Situs inversus
• Teratoma (formed
from epiblast cells –
contain hair, skin,
bone, liver etc cells)
• Caudal dysgenesis
http://radiopaedia.org/cases/sit
us-inversus-9
https://beyondthed
ish.wordpress.com/
2013/05/
http://body-system-broadcast.wikispaces.com/Musculo-Skeletal+System
LCSC06 | Biosciences for SLT
WEEKS 3 TO 4
• Formation of the neural and gut
tubes
• Embryo transformed from a
trilaminar disc into something more
recognisable!
LCSC06 | Biosciences for SLT
NEURULATION
• Formation of neural
plate
• Elevation and curling
of lateral edges
• ‘zippering’ and
formation of the
neural tube
neurulation video
https://en.wikipedia.org/wiki/Neural_tube_defect
,_folate-sensitive
LCSC06 | Biosciences for SLT
NEURAL CREST
http://www.intechopen.com/books/neuroblastoma/
LCSC06 | Biosciences for SLT
FINAL DESTINATION NEURAL
CREST CELLS
• Connective tissue and bones of the face and
skull
• C cells of thyroid gland
• Septum of the heart
• Odontoblasts
• Dermis in the face and neck
• Dorsal root ganglia
• Sympathetic chain and pre-aortic ganglia
LCSC06 | Biosciences for SLT
FINAL DESTINATION NEURAL
CREST CELLS
•
•
•
•
•
•
Parasympathetic ganglia of the GI tract
Adrenal medulla
Schwann cells
Glial cells
Arachnoid and pia mater
melanocytes
LCSC06 | Biosciences for SLT
FINAL DESTINATION NEURAL
CREST CELLS
http://sharonap-cellrepro-p3.wikispaces.com/Creating+Bodies
LCSC06 | Biosciences for SLT
WEEK 3: 0.5 MM
https://en.wikipedia.org/wiki/Spina_bifida#/m
edia/File:S a-bifida.jpg
https://en.wikipedia.org/wiki/Somite
LCSC06 | Biosciences for SLT
FOLDING OF THE EMBRYO
• Dorsal surface – formation of the neural tube
– ‘zippering’ effect
– cervical first, then caudally
• Ventral surface – formation of gut tube and
body cavities
• Body stalk – eventual umbilical cord
LCSC06 | Biosciences for SLT
FOLDING OF THE EMBRYO
https://www.studyblue.com/notes/note/n/embryology/deck/3740268
LCSC06 | Biosciences for SLT
FOLDING OF THE EMBRYO
http://philschatz.com/anatomy-book/contents/m46319.html
LCSC06 | Biosciences for SLT
FORMATION OF THE UMBILICAL
RING
• Proliferation and differentiation of mesoderm
• Causes ventral folding along sides of embryonic axis;
amnion surrounds embryo
• Formation of gut tube
• Brain grows
• Head and tail folding
• ‘purse strings’ effect
folding of the embryo in two planes
LCSC06 | Biosciences for SLT
Week 4 embryo
http://pregnancyweeks.wikispaces.com/
Your+Baby%E2%80%99s+Development+
and+Improvement+in+Week+4+of+Preg
nancy
LCSC06 | Biosciences for SLT
ONTOGENY REPLICATES
PHYLOGENY
LCSC06 | Biosciences for SLT
ONTOGENY REPLICATES
PHYLOGENY
https://en.wikipedia.org/wiki/Recapitulation_theory
LCSC06 | Biosciences for SLT
NEURAL CREST CELLS: IN THE
HEAD AND NECK REGION……
• Form ganglia of the cranial nerves
• Connective tissue and some of the bones of
the skull and face
• Dermis in the face and neck
• Odontoblasts
• Arachnoid and pia mater
• Glial cells
LCSC06 | Biosciences for SLT
https://www.studyblue.com/notes/note/n/embryology/deck/3740268
LCSC06 | Biosciences for SLT
WEEK 3: 0.5 MM
https://en.wikipedia.org/wiki/Somite
LCSC06 | Biosciences for SLT
FATE OF THE MESODERM
• Paraxial mesoderm forms paired somites
from occiput caudally along the length of
the neural tube
• In the head region, somitomeres form
part of skull, muscles, vertebrae, and
dermis of the skin.
LCSC06 | Biosciences for SLT
DEVELOPMENT OF THE SKULL
• Neurocranium (protective covering of the brain)
derived from paraxial mesoderm
– Membranous portion (flat bones)
– Cartilagenous portion = Chondrocranium (base of
the skull)
• Viscerocranium (skeleton of the face – the ‘middle
third’ - & including the mandible) derived entirely
from neural crest cells
LCSC06 | Biosciences for SLT
DEVELOPMENT OF THE SKULL
viscerocranium
http://medical-dictionary.thefreedictionary.com/neurocranium
LCSC06 | Biosciences for SLT
DEVELOPMENT OF THE BRAIN
VESICLES
•
•
•
•
•
Cranial end of neural tube expands
Neural tube closure complete in week 4
Brain vesicles form the future brain
Anterior vesicle: prosencephalon
This subdivides: telencephalon (future cerebral
hemispheres) and diencephalon (optic and thalamic
tissues and other structures)
LCSC06 | Biosciences for SLT
www.en.wikipedia.org
LCSC06 | Biosciences for SLT
PRIMARY BRAIN VESICLES
(rhombencephalon)
https://en.wikipedia.org/wiki/File:EmbryonicBrain.svg
LCSC06 | Biosciences for SLT
PRIMARY BRAIN VESICLES
http://bookcoverimgs.com/fetal-brain-development-stages/
LCSC06 | Biosciences for SLT
FURTHER DEVELOPMENT OF THE
NS
• The nervous system continues to develop and
changes occur up until the early 20’s
• The main changes include:
• Myelination
• Formation of synapses
• Synaptic pruning
• Apoptosis
LCSC06 | Biosciences for SLT
SYNAPTIC PRUNING
• Microglia -nerve cells which are usually
involved in response to injury in the NS
• They also pluck off or ‘prune’ some of the
synapses between neurons
• In conjunction with apoptosis of neurons,
ensures that only the most-used ie
strongest connections, remain
• Keeps the brain operating efficiently
LCSC06 | Biosciences for SLT
SYNAPTIC PRUNING OCCURS
• Prenatally
• In childhood
• At puberty
• “use it or lose it”
• Learning causes synaptic connections to
increase in strength
LCSC06 | Biosciences for SLT
IMPLICATIONS FOR SLT
• Aberrant synaptic pruning may be at the
root of MND, MS
• AD – by the time it is identified, people
have lost over HALF their synapses
• Children with ASD have increased cerebral
volume, ? ? have not undergone the same
extent of synaptic pruning?
LCSC06 | Biosciences for SLT
MYELINATION
• Starts late in embryonic development
and continues into adolescence/early
adulthood
• Forebrain the last part to complete
myelination
• Q what is the function of the myelin
sheath?
LCSC06 | Biosciences for SLT
THE SPINAL CORD
• Extends from the foramen magnum to the level
of the second lumbar vertebra
• Shorter than the vertebral column because it
does not grow as rapidly during embryonic
development.
• Because the spinal cord is shorter, spinal nerves
do not always exit the vertebral column at the
same level as their origin in the spinal cord.
LCSC06 | Biosciences for SLT
THE SPINAL CORD
https://quizlet.com/24950848/spinal-cord-flash-cards
https://it.wikipedia.org/wiki/Cauda_equina
LCSC06 | Biosciences for SLT
BY THE END OF THE 4TH WEEK
• Neural folds have closed
• Head region distinguished by presence of 3
brain vesicles
• Lens and otic placodes for eye and ear
development;
• Primitive oral cavity (stomatodeum)
• 3 pairs of pharyngeal arches
LCSC06 | Biosciences for SLT
BY THE END OF THE 4TH WEEK
http://pregnancyweeks.wikispaces.com/Your+Baby%E2%80%99s+
Development+and+Improvement+in+Week+4+of+Pregnancy
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
• Neural crest material grows from the
rhombencephalic region (rhombomeres)
• Migrates and forms 6 paired bands
• These form the pharyngeal arches
• Each is accompanied by its own artery,
nerve and cartilage
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
http://www.med.umich.edu/lrc/cou
rsepages/m1/embryology/embryo/
09faceandpharynx.htm
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
http://center-for-nonverbal-studies.org/pharynx.htm
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
https://commons.wikimedia.org/wiki/File:Phar
yngealArchHuman.jpg
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
https://odontologi.wikispaces.com/cranio-facial+development
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
http://scienceblogs.com/pharyngula/2006/06/21/deep-homologies-in-thepharyng
LCSC06 | Biosciences for SLT
FORMATION OF THE PHARYNGEAL
ARCHES
http://medchrome.com/basicscience/anatomy/generalembryology-mnemonics
LCSC06 | Biosciences for SLT
FIRST ARCH DEFORMITIES
• Micrognathia
• Cleft palate (indirectly)
• Conductive hearing loss
• External ear malformations
LCSC06 | Biosciences for SLT
http://byebyedoctor.com/treacher-collins-syndrome/
ABNORMAL NEURAL CREST
MIGRATION/DIFFERENTIATION
Treacher-Collins
Robin sequence
LCSC06 | Biosciences for SLT
GOLDENHAR SYNDROME
First AND second
pharyngeal
arches
malformed
http://health9.org/goldenhar-syndrome/
LCSC06 | Biosciences for SLT
DEVELOPMENT OF EXTERNAL EAR
http://wps.aw.com/wps/media/objects/443/454121/developmentofexternalear.html
LCSC06 | Biosciences for SLT
DEVELOPMENT OF EXTERNAL EAR
https://syllabus.med.unc.edu/courseware/embryo_images/unit-ear/ear_htms/ear015.htm
LCSC06 | Biosciences for SLT
FORMATION OF THE FACE
development of the head, neck,
face and palate
LCSC06 | Biosciences for SLT
FORMATION OF THE FACE
http://www.med.umich.edu/lrc/coursepages/m1/embryology/embryo/09faceandpharynx.htm
LCSC06 | Biosciences for SLT
FORMATION OF THE PALATE
https://en.wikipedia.org/wiki/Incisive_foramen
https://web.duke.edu/anatomy/embryology/craniofacial/craniofacial.html
LCSC06 | Biosciences for SLT
FORMATION OF THE PALATE
http://praxisprep.wikispaces.com/Cleft+Palate
LCSC06 | Biosciences for SLT
WEEK 8
https://en.wikipedia.org/wiki/Embryo
LCSC06 | Biosciences for SLT