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Lecture 10

BIO210Y5 Lecture Notes - Lecture 10: Muscular Layer, Neuropeptide Y, Ileum

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Sanja Hinic- Frlog

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nutrition is important because it helps in respiration, cellular exchange & wastes
Ingestion: occurs when food enters oral cavity
mechanical processing: in oral cavity + proximal digestive tract
digestion: chemical + enzymatic breakdown
secretion: release of elements that aid digestion
Absorption: movement of elements into interstitial tract.
Compaction: ↑ dehydration of indigestible materials (feces)
Oral cavity lined by oral mucosa
Digestion of carbohydrates + lipids begin here
Mucosa inferior to tongue allows rapid absorption of lipid-soluble drugs
Uvula helps in preventing food entering into the pharynx pre-maturely + entering the
nasopharynx (Swings upwards)
Secretions by tongue

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Tooth decay formation of dental plaque
22.8 + 22.4

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Peristalsis—bolus arrives in digestive sys circular muscles contract behind the bolus
longitudinal muscles contract ahead of bolus contraction in circular muscle layer forces bolus
Swallowing / deglutition = beginning is voluntary, continuation is automatic
1. Buccal phase: begins with compression of bolus against the hard palate
Forces the bolus to oropharynx
Strictly voluntary
Soft palate ↑ -- nasopharynx sealed
Reflex responses initiated
2. Pharyngeal phase: tactile receptors on palates arches uvula stimulated
Motor commands from swallowing center of medulla oblongata – directs pattern of muscle
contraction in pharyngeal muscles
↑ larynx + folding of epiglottis
Palatal muscles elevate the uvula + soft palate blocks entrance of nasopharynx
Force bolus into esophagus
3. Esophageal phase: begins when bolus in forced to the entrance of esophagus
Bolus pushed towards stomach by peristalsis
Upper esophageal sphincter – band of smooth muscle prevents air from entering
Lower esophageal / cardiac sphincter – band of smooth muscle actively contracting prevents
backflow of materials from the stomach
Bolus approaching stomach opening of lower esophageal sphincter triggered
Poorly lubricated/dry bolus—travels slowly, with aid of secondary peristaltic waves.
22.10 22.3
Relaxed sectional view—thin filaments attached to dense bodies, thick filaments scattered around
the sarcoplasm(> myosin heads / thick filament than skeletal/cardiac muscle)
Relaxed superficial view—network of intermediate filaments connect dense bodies, adjacent
smooth muscle cells bound together by dense bodies
Contracted superficial view—dense bodies not arranged in straight lines corkscrew shape while
contraction, sliding between thick + thin filaments
Smooth muscles: assist in mixing and churning (forming chyme in stomach)
Visceral smooth muscles: non-striated, thick and thin filaments scattered (adaptability to change
in length - plasticity)
Rugae: mucosal folds that can flatten to allow stomach to expand
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