Normal Feeding and Swallowing Development Embryological Flashcards
neuroembryology: crucial development of…
communication, cognition, and swallowing functions
neuroembryology: errors in development can lead to…
PFD, dysphagia, and multiple etiologies that result in developmental and/or feeding problems
prenatal development, embryonic period
- by 3rd week, 3 germ layers develop, CNS and cardiovascular system begin to form
- all major organ systems are formed during the 4th to 8th week of development
prenatal development, fetal period: by 24 weeks
- lungs produce surfactant 24-26 weeks: surface active lipid that maintains the opening of the developing alveoli in the lungs
- respiratory system is still very immature (usually cannot sustain life independently): surfactant therapy has helped extreme preterm infants survive in addition to other medical interventions
- period of “variability” typically discussed in preterm infants is discussed in this period of development
prenatal development, fetal period: 26-29 weeks
- lungs are capable of air exchange, but they have difficulty
- CNS is maturing
- rhythmic breathing movements are possible but not present in all infants
- beginnings of temperature control of the body
- eyes are open at the beginning of this period
prenatal development, fetal period: 30-34 weeks
- pupil response to light reflex can be elicited
- by 34 weeks white fat (nutritional reserves) make up 8% of the fetus’s body weight
- body temperature regulation is more stable by 34-35 weeks
prenatal development, fetal period: 35-40 weeks
- by 36 weeks, head circumference and abdomen are about equal (after 36 weeks abdomen circumference may be > head
- 16% of body weight is white body fat
neural tube development
- dorsal induction then occurs when the neural tube is formed and then closes (also known as primary neurulation)
- the neural plate bends upwards by the end of the 3rd week of development
- neural crest begins formation of neural tube
- complete closure of the neural tube happens by the end of the 4th week
- neural tube eventually develops the entire CNS
while it closes, it leaves neural crest cells
- are the precursors to dorsal root (sensory) ganglia for spinal and sensory cranial nerves
- precursors for Schwann cells that create myelin and the automatic nervous system
- eventually develop into the PNS
CNS development
all neurons in the spinal cord and brain are present by the 25th week of gestation
cortex develops after birth
- more dendrites more neural connections grow after birth
- results in developmental norm acquisition in the first year of life
if the neural tube doesn’t develop or close completely during these first 4 weeks of gestation the following may occur
defects of the brain, spinal vertebrae, and spinal cord
types of neural tube defects
- anencephaly
- spina bifida
- closed neural tube defects
anencephaly
- lack of development of cerebral hemispheres
- absent frontal, parietal, and occipital bones
- has anomalies in the cerebellum, brainstem, and spinal cord
anencephaly happens if the upper part of the neural tube does not close entirely
- stunts the development of the upper portion of the brain including the forebrain
- survival is typically only a few weeks
spina bifida
- can be mild to severe
- occurs in about 3 to 4 babies per 10,000 live births
mildest form of spina bifida
spina bifida occulta –> usually does not cause health problems
more severe types of spina bifida include…
- myelomeningoceles
- meningoceles
- lipomyelomeningoceles
- and other less common lesions
meningoceles
occurs when the spinal cord and nerve tissue do not protrude into the sac. lesion is usually covered by skin
myelocmeningcele
- type of “open spina bifida”
- most series form
- a portion of spinal cord and surrounding nerves protrude through an opening in the spine into an exposed, flat disc or sac that is visible on the back
- exposes the baby’s spinal cord to the amniotic fluid
- can be harmful to the baby’s fetal development
myelocmeningcele: can experience serious health problems
- hydrocephalus
- paralysis: severity of paralysis depends on where the opening occurs in the spine
hydrocephalus
an excessive accumulation of fluid in the brain
closed neural tube defects
- can be located at brain or spinal levels, but usually just the spine
- abnormality along the spine: tuft of hair growing out of a dimple of the spine
- pigmented mole
- or a lumbosacral vascular anomaly (hemangioma, port wine stain)
- lipoma
- dimple in lumbosacral region
lipoma
dome of skin with a mass of fatty tissue under it
pharyngeal arches/branchial arches
- human embryos have 5 pairs (numbered in craniocaudal sequence): give rise to face, jaw, ears, and neck
- numbered 1-6, without 5
- errors here result in craniofacial development errors
pharyngeal arches/branchial arches: numbered 1-6, without 5
5 is a short-lived, rudimentary form or may not develop at all in human embryological development
pharyngeal arches
series of externally visible anterior tissue bands that give rise to the early structures of the head and neck
pharyngeal arch 1: artery
maxillary artery
pharyngeal arch 1: nerve
trigeminal (CN V)
pharyngeal arch 1: muscles
muscles of mastication: anterior belly of the digastric muscle, tensor tympani, tensor veli palatini
pharyngeal arch 1: skeletal structures
mandible, maxilla, malleus, incus, zygomatic and temporal bones
pharyngeal arch 2: artery
stapedial corticotympanic
pharyngeal arch 2: nerve
facial (CN VII)
pharyngeal arch 2: muscles
muscles of facial expression, stapedius, stylohyoid, posterior belly of the digastric muscle
pharyngeal arch 2: skeletal structures
stapes, styloid process, lesser cornu of the hyoid, upper part of the body of the hyoid bone
pharyngeal arch 3: artery
common carotid, internal carotid arteries
pharyngeal arch 3: nerve
glossopharyngeal (CN IX), hypoglossal (CN XII)
pharyngeal arch 3: muscles
stylopharyngeus
pharyngeal arch 4: artery
aortic arch (left), right subclavian artery
pharyngeal arch 4: nerve
vagus (CN X), superior laryngeal nerve
pharyngeal arch 4: muscles
cricothyroid, pharyngeal plexus
pharyngeal arch 4: skeletal structures
laryngeal cartilages: thyroid, cricoid, arytenoid, corniculate, and cuneiform cartilages
pharyngeal arch 6: artery
pulmonary artery (partial left and right)
pharyngeal arch 6: nerve
vagus (CN X), recurrent laryngeal nerve
pharyngeal arch 6: muscles
intrinsic muscles of the larynx, striated muscle of the esophagus: pharyngeal plexus
pharyngeal arch 6: skeletal structure
laryngeal cartilages: epiglottis, thyroid, cricoid, arytenoid, corniculate, and cuneiform cartilages
development of the face
major development between the 4th and 10th week of embryological development
development of the face: achieved by the development and joining of 5 prominences
- frontonasal prominence
- 2 maxillary prominences
- 2 mandibular prominences
- mesenchyme in the facial prominences
frontonasal prominence
- forehead and the dorsum apex of the nose
- lateral nasal prominences and medial nasal prominences
lateral nasal prominences
sides (alae) of the nose
medial nasal prominences
nasal septum
2 maxillary prominences
upper cheek region, majority of upper lip
2 mandibular prominences
chin, lower lip, lower cheek regions
mesenchyme in the facial prominences
fleshy derivatives and bones
errors in facial development: Treacher Collins
disruptions of pharyngeal arches 1 and 2 results in the interruption of the development of the lower face and mandible
palate development
- forms during 5th-7th week
- primary palate is formed by maxillary portions of 1st pharyngeal arch and frontonasal prominence
primary palate is formed by maxillary portions of 1st pharyngeal arch and frontonasal prominence
- includes medial portion of the upper lip and premaxilla
- premaxilla is wedge-shaped mass of tissue that contains incisors and extends posteriorly to the incisive foramen includes the anterior palate and alveolar ridge
- fusion of palate begins at incisive forament and moves forward to the lip
palate development: weeks 7 and 8
- maxillary process produces palatal processes
- palatal processes grow vertically down and parallel to the lateral surfaces of the tongue
palate development: week 8
- 2 vertical shelves of bone that are the palatal processes lift and fuse at midline
- incisive foramen is where primary and secondary palate meet
2 vertical shelves of bone that are the palatal processes lift and fuse at midline
- fusion is called: medial palatine suture or intermaxillary suture
- the fusion of the palatal processes from the secondary palate
- in order for the shelves to elevate and close off the mandible must grow down and forward to lower the tongue or the palate will not fuse (cleft)
prenatal and neonatal reflexes
- pharyngeal swallow (10-12 weeks)
- suckling (18-24 weeks)
- gag (26-27 weeks)
- lingual cupping (27-29 weeks)
- rooting (28 weeks)
- phasic bite (40 weeks)
- suck-swallow-breath (34-35 weeks)
swallowing and sucking in utero
- pharyngeal swallow is 1 of first motor responses in the developing pharynx
- non-nutritive sucking and swallowing is seen via US by most fetuses by 15 weeks GA
- true suckling (in and out A-P tongue movement) begins around 18th-24th week
- consistent swallowing of amniotic fluid seen by 22-24 weeks
- 34th week
- sucking frequency increased in the later months of fetal development (impacted by taste)
- taste buds develop at 7 weeks, mature receptors by 12 weeks
- decreased rates of fetal suckling are associated with obstruction (aerodigestive tract), neurological damage, and may manifest of IUGR
- estimates that 450 mL of total 850 mL of amniotic fluid produced daily is swallowed in utero
pharyngeal swallow is 1 of first motor responses in the developing pharynx
- between 10-14 weeks GA
- pharyngeal swallows seen in fetuses 12/5 weeks gestation
swallowing and sucking in utero: 34th week
most have a mostly mature suckle and swallow to sustain PO (if health, but not all)
anatomical differences infants vs. adults
- no teeth
- large tongue
- fat pads
- flat hard palate
- velum fills gap
- hyoid and thyroid are besties!
- larynx positioned higher
- obligatory nose breathers
oral cavity: infant
- tongue fills mouth
- edentulous
- tongue rests between lips and sits against palate
- cheeks have sucking pads (fatty tissue within buccinators)
- relatively small mandible
- sulci important in sucking
oral cavity: older child
- mouth is larger
- dentulous
- tongue rests on floor of mouth
- tongue rests behind the teeth and is not against palate
- buccinators are muscles for chewing
- mandibular-maxillary relationship relatively normal
- sulci have little functional benefit
pharynx: infant
- no definite/distinct oropharynx
- obtuse angle at skull base in nasopharynx
pharynx: older child
- elongated pharynx, so distinct oropharynx exists
- 90 degree angle at skull base
larynx: infant
- one-third adult size
- half true vocal fold of cartilage
- narrow, vertical epiglottis
- high in the neck, re: cervical vertebrae
larynx: older child
- less than one-third true vocal fold of cartilage
- flat, wide epiglottis
- by 2 years of age, approximates adult position re: cervical vertebrae
sensory system and swallowing
- gustatory
- olfactory
- tactile
medical factors and feeding/swallowing
- developmental
- neurological
- GI
- cardiopulmonary
- upper airway
- genetics
medical co-morbidities: neurologic
- enceophalopathies (cerebral palsy, perinatal asphyxia)
- traumatic brain injury
- neoplasms
- intellectual disability
- developmental delay
medical co-morbidities: anatomic and structural
- congenital: tracheoesophageal fistula and esophageal atresia, cleft palate
- acquired: tracheostomy, vocal fold paralysis or paresis
medical co-morbidities: genetic
- chromosomal: Down syndrome
- syndromic: Pierre Robin sequence, Treacher Collins syndrome, CHARGE syndrome
- inborn errors of metabolism
medical co-morbidities: secondary to systematic illness
- respiratory: bronchopulmonary dysphagia, chronic lung disease of prematurity, bronchopulmonary dysplasia
- gastrointestinal: inflammatory conditions, GI dysmotility, constipation
- congenital cardiac anomalies
medical co-morbidities: psychosocial and behavioral
- oral deprivation
- secondary to unresolved or resolved medical condition latrogenic
