Lecture 38 Flashcards
Digestive system
Structure Irregular tube Open at both ends – ‘outside’ the body! Alimentary canal or gastrointestinal (GI) tract Organs (see Box in Textbook)
Functions
Digestion
Absorption
Metabolism
Walls of the GI tract
Four layers of tissue
Structure varies among organs
From inside to outside, they are:
Mucosa
Submucosa
Muscularis
Serosa
Mucosa layer
Production of mucus to coat lining of ‘tube’.
Secretion of digestive enzymes and hormones
Absorption of the end products of digestion
Protection against pathogens
Submucosa layer
Connective tissue layer
Contains glands, blood vessels, lymphatic vessels, & parasympathetic nerves
Contains lots of elastic fibres, allowing the tube to stretch and recoil (especially the stomach)
Muscularis layer
Mixes & churns food Peristalsis Consists of 2 or 3 layers (depending on location in GI tract): 1Inner circular (lots at sphincters) 2Outer longitudinal 3Oblique
Serosa layer
Protective outermost layer
Composed of visceral and parietal peritoneum in abdominal cavity
Mouth (oral/buccal cavity)
Where process of digestion begins!
Hollow ‘chamber’ Lined with mucosa 3 ‘parts’: Roof Floor Walls
Mouth roof
Hard palate (2 maxillary & 2 palatine bones)
Soft palate (arch-shaped muscle; separates mouth from nasopharynx)
Uvula – projection of soft palate
Uvula & soft palate prevent food & liquid from entering nasal cavities
Floor of mouth
Tongue and its muscles
Tongue is skeletal muscle, and is anchored to floor of mouth by the frenulum
Consist of a tip, a body and a root
Small nipple-like projections on tongue, called papillae
Taste buds found in many papillae
Ankyloglossia
Tongue tied
Frenulum is unusually short and thick
Can be mild (bands) to complete (entire tongue is attached to the floor of the mouth)
Affects feeding/eating, swallowing, oral hygiene/structure, speech
May recede on its own; surgery is an option
Mouth walls
Lateral walls formed by the cheeks (buccinator muscle); contain mucous-secreting glands
Anterior wall formed by the lips
Skin on outside, mucous membrane on inside; junction highly sensitive
Line of contact between closed lips = oral fissure
Salivary glands
Function:
Secrete approximately 1 litre of saliva (salivary amylase + mucus) each day!
Parotid glands (largest) Submandibular glands (‘below mandible’) Sublingual glands (‘below tongue
Parotid glands
Largest
Bottom of ear at jaw angle
Ducts secrete into mouth cavity
Function:
Produce watery saliva containing enzymes
Submandibular glands
Middle of mandible
Ducts secrete on either side of lingual frenulum
Function:
Contain enzyme- and mucous-producing substances
Sublingual glands
Anterior to submandibular glands
Ducts secrete into floor of mouth
Function:
Produce a mucus type of saliva