What are the basic processes of digestion?
- ingestion
- mechanical and chemical digestion
- absorption
- elimination
secretion, mixing and propulsion
How is food broken down?
Physically- chewing and grinding
Chemically- enzymes in the stomach and small intestine
- microbes in the stomach and large intestine
Describe a simple digestive tract.
- Mouth
- Pharynx
- Oesophagus
- Stomach
- Small Intestine
- Large intestine
- Rectum
What are the related structures of the digestive system?
Salivary glands- enzymes eg; lysozyme and amylase
Pancreas- secretes hormones and enzymes into the small intestine
Liver- forms bile and secretes it into the small intestine via the sphincter
What are the parts of the mouth?
Lips cheeks hard and soft palate tongue teeth pharynx oesophagus
What is the function of the tongue?
mastication
taste
thermoregulation
papillae for grooming
What are teeth made up of?
above gum; - enamel - dentine - pulp below the gum; - root - neck - crown - alveolus - periodontium
What are the functions of the incisors?
- cutting and grasping
What are the functions of the canines?
tering and grasping
What are the functions of the premolars?
sharp edges for crushing
grinding surface
What are the functions of the molars?
grinding
What happens in swallowing?
- soft palate rises
- epiglottis lowered to close trachea
- pharynx directs food into the oesophagus aided by the tongue
- peristalsis propels food down towards the stomach
What are the three phases of swallowing?
Buccal Phase- voluntary
Pharyngeal phase- involuntary
Oesophageal phase- involuntary
What is tunica mucosa?
epithelium connective tissue (muscular mucosa)
What is tunica submucosa?
loose connective tissue
blood vessels
nerves
What is tunica muscularis?
smooth muscle
nerve fibre network
What is tunica serosa or adventitia?
serosa- abdominal cavity membrane that secretes serous fluid eg; liver, spleen and stomach
adventicia- loose connective tissue or retroperitoneal organs eg; kidney, bladder aorta or oesophagus
What is the oesophagus?
collapsible muscular tube
bolls into stomach
made up of tunica mucosa, submucosa, adventitia, muscularis
What secretory epithelial cells cover the lining of the stomach?
- Mucous cell; secrete alkaline mucous to protect the epithelium against stress
- G cells; secret hormones gastrin and stimulates parietal and chief cell contractions
- Parietal cells; secrete hydrochloric acid and intrinsic factor
- Chief cells; secrete pepsinogen
