pt 1 anatomy, embryology, physiology, and typical development

the most complex neuromuscular unit in the body

upper aerodigestive tract

serves as the shared pathway for the digestive, respiratory, and phonatory systems

upper aerodigestive tract

Normal Swallowing requires integration of the important functions of

breathing, eating, and speaking.

Understanding ______, ______, and ______ changes from infancy to adolescence is critical and informs diagnosis and treatment of pediatric feeding and swallowing disorders.

anatomy, physiology, and developmental

what structure is crucial for respiration, especially in neonates & infants (preferential breathing)

nose (nasal breathing)

nose functions:

cleans, warms, humidifies inspired air

the nose opens into nasopharynx via bilateral posterior nasal choanae—important for

speech resonance and airway

Lateral walls of the nose have nasal turbinates covered with _________

sensitive mucosa

nose is separated by

midline septum

Septal deviation at birth can cause ________ → feeding difficulties.

nasal obstruction

seals nasal cavity from oral cavity during swallowing.

soft palate elevation

Other causes of nose obstruction:

choanal atresia, encephalocele, rhinitis, etc.

what structure is involved in food ingestion, vocalization, and oral respiration.

mouth

Cheeks with _____ important for sucking in infants.

fat pads

______ affect sucking & swallowing

Anatomic defects

Food/liquid can lodge in __________ affecting bolus prep

anterior & lateral sulci

In infants, what structures blend?

nasopharynx and hypopharynx blend; no distinct oropharynx

Swallowing initiation is _____; completion is _____

voluntary; involuntary

• Drains sinuses & middle ear

• Resonator for speech

• Sealed off during swallowing via soft palate elevation

nasopharynx

Includes:

• Palatine tonsils (between tonsillar pillars)

• Valleculae (wedge-shaped spaces at tongue base & epiglottis)

• Lingual tonsil (at tongue base; enlargement may impair airway/swallowing, linked to GERD/EERD)

oropharynx

Part of the common airway-foodway intersection

hypopharynx

Key role in directing food to esophagus, away from airway

hypopharynx

Tonic contraction at rest—prevents reflux & air entry

Cricopharyngeus Muscle (UES) Upper Esophageal Sphincter

Cricopharyngeus Muscle (UES) Upper Esophageal Sphincter Relaxes only during:

• Swallowing

• Belching

• Regurgitation

Primary Functions (in order of priority) of the larynx

• Airway Protection

• Respiration

• Phonation

protective mechanisms of the larynx

• Epiglottis: Directs food laterally into pyriform sinuses

• Arytenoid cartilages + Aryepiglottic folds: Medial movement blocks laryngeal inlet

• False vocal folds (ventricular): Expiratory control

• True vocal folds: Prevent inspired foreign materia

Propels food from hypopharynx to stomach

esophagus

Upper Esophageal Sphincter (UES) → ______ muscle

Cricopharyngeus muscle

what structure of the esophagus: tonic contraction at rest; prevents air ingestion

UES

Lower Esophageal Sphincter (LES) →

Junction with stomach

what structure of the esophagus: Transient relaxation; prevents gastric reflux

LES

Help maintain an empty esophagus between swallows

LES

comparison of infant toddler and older adult

formation of 3 germ layers by week __

3

• ectoderm

• mesoderm

• endoderm

CNS & cardiovascular system begin forming week ____

Week 3-4

All major organ systems develop at week ____

week 4-8

Embryo takes on human appearance by Week __

8

Rapid growth; face forms; limb development

week 9-12

Skeleton ossifies; movement felt by mother

weeks 13-20

Weight gain; lungs begin surfactant production weeks ____

weeks 21-25

Lungs can exchange air; eye opening; temperature control begins

weeks 26-29

Weeks ___: Pupillary reflex present; white fat → feeding readiness

weeks 30-34

Growth finalizes; ready for birth at ~38 weeks post-fertilization

weeks 35-40

Pharyngeal swallow appears by ____ weeks gestation

10–14

Swallowing observed in fetuses as early as ___ weeks

12.5

Non-nutritive sucking seen by __ weeks via ultrasound

15

Suckling (early feeding pattern) begins ___ weeks

18–24

Tongue moves forward & backward (more backward force)

suckling

Sucking (more mature pattern) emerges at ~________

4 months postnatal

Tongue moves up/down; lips more active

sucking

Consistent swallowing by ____ weeks

22-24

By ____ weeks, many fetuses can suckle and swallow adequately for oral feeding

32–34

why is understanding the development of the CNS important?

CNS regulates swallowing (buccal, lingual, pharyngeal)

Fetal facial expressions visible via 4D ultrasound by ____ weeks

20–24

The most critical period for brain development is from ____ weeks, however disruptions can occur after this period

3 to 16

four types of embryologic abnormalities

malformation, disruption, deformation, dysplasia

causes of embryologic abnormalities

genetic, environmental, or both; major cause of feeding/swallowing disorders

Teratogens (e.g., drugs, viruses) are most harmful ___ weeks gestation

3–16

Impact of embryologic abnormalities depends on

• Critical developmental period

• Dosage

• Embryonic genotype

Injuries during early gestation cause greater long-term damage due to:

immature blood-brain barrier, development depends on integrity of early structures

Low birth weight and prematurity

• Survival is rare <___ g or <____ weeks

• CNS & respiratory system mature significantly by __ weeks

• _______ abnormalities (CNS, airway, GI, etc.) may co-occur

• 500; 22–23

• 28

• Multisystem

5 key phases of swallowing

1. Oral Preparatory Phase (Bolus Formation)

2. Oral Transit

3. Initiation of Pharyngeal Swallow

4. Pharyngeal Phase

5. Esophageal Transit

voluntary control

Oral preparatory & oral transit

mixed control

Pharyngeal phase

involuntary control

Esophageal phase

oral prep and oral transit includes:

• Feeding (self or assisted)

• Manipulation of food/liquid in the mouth

Bolus formation begins at what phase?

oral prep and transit

bolus prep for infants

latching and sucking (minimal bolus prep)

Food texture & oral skill level impact _____ of oral prep and transit

duration

structures involved in oral prep and transit

• _______ is needed once material is in the mouth so that no liquid or food will be dribbled down the chin

• The material is then held between the ______and ______

• The ____________ help to generate suction in neonates and hold food between the teeth in older infants and children.

• During this process, the _________ is in a lowered position and resting against the tongue base. This position helps to prevent a bolus from entering the pharynx before the swallow is produced.

• The airway remains open and nasal breathing continues until a pharyngeal swallow is initiated

• Lip closure

• elevated tongue and hard palate

• buccinator muscles

• soft palate

initiation of pharyngeal swallow may occur at what structures for infants:

• Anterior tonsillar pillars

• Base of tongue

• Valleculae

• Pyriform sinuses

Essential for normal bolus formation and transit

pharyngeal swallow initiation

Sensory input of pharyngeal swallow drives motor modulation via ________

brainstem pathways

Types of Sensory Receptors for pharyngeal swallow initiation

• Mechanoreceptors: touch, pressure (e.g., in tongue, palate, teeth)

• Nociceptors: pain detection

• Proprioceptors: sense shape, position

• Chemoreceptors: detect chemical composition

• Special receptors: for taste, smell, temperature

6 steps of pharyngeal swallow function

1. Elevation/retraction of soft palate (nasopharynx sealed)

2. UES opening (passive, via anterior laryngeal movement)

3. Laryngeal closure (vestibular level)

4. Tongue ramping/loading

5. Tongue propulsion

6. Pharyngeal clearance