digestve system

What is ingestion?

Taking in food

What is digestion?

Conversion of large molecules → smaller ones

What is absorption?

Though walls of tract → blood + lymph

What is excretion?

Expulsion of non absorbed materials

What os peristalsis?

Involuntary muscle contractions to move food along digestive tract

How many of each teeth are in an adult set?

• 8 incisors

• 4 canine

• 8 premolar

• 12 molars

Describe the enamel on teeth

Hard + mineralised

Describe the dentin on teeth?

Soft + decay prone

Describe cementum on teeth

Specialised bone like structure, covers root

Describe pulp on teeth

• Soft connective tissue

• Has blood supply + nerves

Describe the structure of the tongue

• mass of striated muscle

• Covered in mucous membrane

• Seperated by median septum

Wha are the 3 parts of the tongue?

Oral - anterior

Pharyngeal - posterior

Root - base

What’s the name of the 2 tongue surfaces?

1. Dorsal

2. Ventral

What is the role of the intrinsic tongue muscle?

Alters shape of tongue

What is the structure of the intrinsic tongue muscles?

• no bony attachment

• Longitudinal/ transverse/ vertical fibres

What is the role of the extrinsic tongue muscles?

Helps move the tongue

What is the structure of the extrinsic tongue muscles?

• connects to surrounding structures

1. Palatoglossus

2. Genihydois

3. Geniglossus

4. Hyoglossus

5. Styloglossus

What’s are the salivary glands/ what do they produce?

1. Parotid- salivary amylase

2. Submandibular- buffers, glycoproteins, mucins + salivary amylase

3. Sublingual- mucous

What are the contests of saliva?

• water

• Salivary amylase

• Mucin

• Lysosyme

What is the role of saliva?

• lubrication

• Solubilisation

• Starch digestion

Describe the oesophagus

• soft muscular tube

• Allows food from pharynx → stomach

What is tHe position of the oesophagus?

• anterior to spine

• goes through neck, chest +. Abdomen

What is the role of the oesophageal sphincters?

Prevents backflow

Where is the upper oesophageal spichnter located?

• between pharynx + oesophagus

• C5-C6 level

What is the upper oesophageal spnchicteb made of ?

• Muspclocartilginous , cricopharynxgeus fibres

Where is the lower oesophageal sphincter found?

Where the oesophagus meets the stomachs

What are the GI tract layers

1. Lumen

2. Inner mucosa

3. Submucosa

4. Muscilarus

5. Adventia

What is within the inner mucosa?

• Epithilum

• Lamina propria

• Lymphoid aggregates

• Muscularis mucosae

Describe the stomach?

Capacity and for how long

• muscular sac

• 50ml- 5L capacity

• Holds food for 3-4 hours

What is the roe of the stomach?

• short term storage

• Mixes and churns food (Form chime)

• Digest proteins (pepsin)

• Absorb some substances

What is the 3 parts of the stomach?

1. Fundus

2. Body

3. Plyorus

Name of place where oesophagus meets stomach?

Cardia

Describe gastric rugae

• thick mucous membrane Folded

• Lined with simple columnar cells (secrete mucin)

What are the gastric glands types + secretions?

1. Cardiac (mucin)

2. Fundus and body (acidic juices + mucin)

3. Plyorus (mucin and Gastrin)

Where are the gastric glands found?

In teh mucous membrane of the stomach

What gastric gland is lowest in number?

Cardiac

Wha gastric gland is highest in number?

Fundus and body

What does the surface mucosa and mucous neck cell secrete in the gastric pit?

Mucus

What does the parietal cell secrete in the gastric pit?

Hydrochloric acid + intrinsic factor

What do chef cells secrete in the gastric pit?

Pepsinogen and gastric lipase

What does G cells secrete in gastric pits?

Gastrin

How much gastric juice do we serve a day?

1-1.5L

What is the pH of Gastric juice?

0.9- 1.5

What is the role of hydrochloric acid in the stomach?

• convert pepsinogen → pepsin

• Stimulate hormone secretion from small intestine

Where are the types of pepsinogen found?

1. Pepsinogen I- Fundus + body

2. Pepsinogen II- whole stomach

How does pH effect pepsin?

• pepsinogen → pepsin at pH6

• Best at pH 1.5-3.5

• In active at pH9

What does pepsin rue protein to?

Peptones

How is mucin protected from acid-peptic digestion?

Carbohydrate coat over surface

Describe mucin

Insoluble or soluble glycoproten that acts as HCL defence

What is the main nerve of teh GI tracts and stomach?

Vagus nerve

What is the role of efferent nerve fibres?

• glandular secretions

• Relaxation/ contraction of muscles

What is the role of adherent nerve fibres?

Hunger + nausea

What is the ingest part of the GI tract?

Small intestine

What is the name of the liquid form the stomach?

Chyme

Name the 3 regions of the small intestine and their length

1. Duodenum- 25cm

2. Jejunum- 2.4m

3. Illum- 3.5m

What are the villi cell types and their functions?

• enterocytes- absorption

• Goblet cells- mucus production

• Endocrine cells - secretin + CCK production

• Stem cells

Where is the pancreas found?

• beneath the stomach Connects

• Connects to small intestine by pancreatic duct

What type of cells are found in teh pancreas?

• endocrine and exocrine

What is found in pancreatic fluid?

• sodium bicarbonate

• Pancreatic amylase

• Pancreatic lipase

• Nuckeases

What is the role of nucleases in teh pancreas?

Hydrolise. Nucleic acid → nucleotides

What is the role of pancreatic lipas in teh pancreas ?

• break triglycerides → fatty acid + glycerol

• TG’s synthesis in epithelial cells + combine with proteins (chclomicrons)

• Diffuse to nucleic acid

What is teh role pf pancreatic amylase?

• starch digestion

• Diasacharides→ monosaccharides

• Absorbed by epithelial cells → blood

What is the role of bicarbonate in the pancreas?

• neutralise fluid from stomach

What are the protein digesting pancreatic enzymes

• tripsin

• Cymotripsin

• Carboxypeptidase

• Elastase

Describe the structure of the gall bladder

Muscular pouch

Lined by simple epithelium

Stores bile

What happens at the large intestine?

• receives material after digestion + absorption

• Mostly water and undigested material (cellulose)

How are faeces released?

• relaxing anal spchiter

• Contraction of diaphragm and abdomen

What causes diarrhoea?

Discharge before water reabsorption

What causes constipation?

Faeces Retained too long

Dries out