Digestive system Flashcards
(35 cards)
What are the 6 functions of the digestive system
Ingestion
Mechanical processing
Digestion
Secretion
Absoprtion
Excretion
What is the peritoneum and what does it do
A serous membrane that lines abdominal cavities - with visceral layer covers the organs, with the parietal layers lining the cavities.
It secretes peritoneal fluid, which lubricates for the sliding of food
What are mesenteries
A fold of membrane that attaches the intestine to the wall around the stomach area and holds it in place.
Allowing for passage of blood vessels, nerves and lymphatic vessels.
What is the digestive tracts function
To move (and absorb in some parts) food whilst protecting against:
- Digestive acids and enzymes
- Mechanical stresses
- Bacteria
What are the 4 layers of the digestive tract
Mucosa, submucosa, muscularis externa and the serosa
What does the mucosa layer do, and its three layers
Is the inner layer responsible for absorption of nutrients, secretion of digestive fluids, and acting as a barrier against harmful substances.
Mucosal epithelium, lamina propria and muscularis mucosae
What does the submucosa layer do
Supports the mucosa by containing large blood and lymphatic vessels. Is made of dense irregular connective tissue
What does the muscularis externa layer do
This conducts perisatlisis - coordinated movements by the enteric nervous system
Consists of smooth muscle in: inner circular layers and outer longitudinal layers
What does the serosa layer do
a serous membrane that secretes fluid to reduce friction on the OUTER side of digestive organs
How is the movement of material controlled
By rhythmic cycles of smooth muscle activity controlled by pacemaker cell which are located in the muscularis mucosa and externa.
The cells undergo spontaneous depolarization and peristalsis (waves of muscular contraction).
What does the oral cavity do (5)
Sensory analysis
Mechanical processing
Lubrication
Limited digestion (mainly carbs and lipids
Passageway for food, liquid and air
How does lipids and carbs digest in the oral cavity
Carbohydrates through salivary amylase and lipids through lingual lipase produced by the tounge
What is salivas function (3)
Lubricating the mouth and its contents, dissolving chemicals, initiating digestion of complex carbs by salivary amylase
What salivary glands produce what
Parotid = serous secretions
Sublingual = mucous
Submandibular = buffers, glycoproteins and salivary amalyase
What is the 4 step process of swallowing
Buccal Phase
Pharyngeal phase
Osephageal phase
Bolus enters the stomach
What does the oesophagus do
Conveys solid food and liquids to the stomach
What prevents air from entering the oesophagus
resting muscle tone in the superior 3 cm, which is anchored in place by adventitia anchors to the surrounding structures
What does the stomach do
Is involved majorly in storage of ingested food, as well as the mechanical and chemical breakdown
How is food chemically broken down in the stomach
Occurs via enzymes (started by pepsin and continued by salivary amylase and lingual lipase) and by acids (HCI) which reduces the pH to 2
Also produces an intrinsic factor, that is needed fro vitamin b12 absorption
What does the stomach lining include
Simple columnar epithelium – which lines the stomach and produces mucus.
Gastric pits – which connect the gastric bands in the mucosa onto the gastric surface.
Smooth Muscle – includes the muscularis mucosae and the muscularis externa. Has an oblique layer in addition to circular and longitudinal layers
What are the glands in the stomach
Gastric glands = found in the fundus and body of the stomach
Pyloric glands = found in the plyorus
What do gastric glands do (3)
They contain paretial cells which secrete an intrinsic factor and hydrochloric acid.
AS well as cheif cells which secrere pepsinogen and convert pepsin to Hydrocholric acid
Also G cells that secrete gastrin
What are the 3 regions of the small instestine, and what happens in them
Duodenum - receives chyme, and digestice secretions and neutralises it
Jejunum = Site of most chemical digestion and nutrient absorption
Ileum = Has lymphoid nodules which are part of the immune system
What are key feautres of the small intestine
Intestinal glands = Secretes enzzymes into the lumen, also have brush border enzymes which break down material they come into contact with.
Dueodenal glands = which produce mucus and raise pH
Intestinal juice = moistens chyme and keep contents a solution, and buffers the acid
