The Digestive System Flashcards
Describe the arrangement of the organs and the peritoneum
- PELVIC ORGANS - covered on superior surface
- STOMACH AND INTESTINES - invaginated behind and completely surrounded with a double fold (attached it to abdominal wall)
- PANCREAS, SPLEEN, KIDNEYS and ADRENAL GLANDS - invaginated from behind and pushed against abdominal wall
- THE LIVER - invaginated from above, almost completely covered, attached to diaphragm
- BLOOD VESSELS - pass close to the abdominal wall and send branches to the organs between the peritoneum
What are the specialise areas of the peritoneum?
- MESENTRY - a double layer of visceral peritoneum that attaches an organ to the body wall
- OMENTUM - a double layer of visceral peritoneum that attaches one organ to another
- PERITONEUM CAVITY - between the visceral and parietal - contains serious fluid
What is the function of the mouth?
- Bound by muscles and bones
- Lined with mucous membranes consisting of stratified squamous epithelium containing small mucus-secreting glands
- teeth are used for grinding and chewing
- The tongue plays an important part is mastication, deglutination (swallowing), speech and taste
What is the structure and function of the salivary glands
3 main parts (glands):
PAROTID - either side of mouth
SUBMANDIBULAR - on each side of face, under the jaw
SUBLINGUAL - under mucous membranes of the floor of the mouth.
- Chemical digestion of polysaccharides (complex sugars and starch)
- Lubrication of food
- Cleaning
- Non-specific defence (lysosome, immunoglobuns and clotting factors)
- Taste
What is the structure and function of the pharynx
3 parts - nasopharynx, orapharynx and laryngopharynx
- food passes from oral cavity into the pharynx then to the oesophagus below.
What is the structure and function of the oesophagus?
4 layers of tissue: MUCOSA SUBMUCOSA MUSCULARIS EXTERNA SEROSA The functions of the mouth, pharynx and oesophagus together are the formation of bolus and swallowing
What is the structure and function of the stomach
Continuous with the oesophagus at the cardiac sphincter and with the duodenum at the pyloric sphincter.
- when the stomach is relaxed the pyloric sphincter opens and vice versa.
- Functions: storage, chemodigestion, mechanical breakdown and defence hormones
What are the main cells of the stomach and what do they do
- PARIETAL CELLS - secrete HCl and intrinsic factors to acidity the food and stop the actions of salivary amylase. Also kills microbes and activates pepsinogen.
- CHIEF CELLS - secrete pepsinogen which is activated into pepsin which is important for protein digestion!
- ENTEROENDOCRINE CELLS - secrete Gastrin stimulates the production of HCl and pepsinogen and also increases stomach motility and secretion
What is the structure and function of the liver
- Lies in the hypochondrium and epigastrium.
- very large organ with 4 lobes!
- important in bile production and metabolism.
What is the structure and function of the gall bladder
- Sack-like structure
- Stores and concentrates bile
- Bilary tree shows movement of bile between the liver, duodenum and gall bladder
What is the structure and function of the pancreas
- Retroperitoneal - sits in curve of duodenum
- has head, body and tail!
- EXOCRINE -
- Secretes 1.5L of pancreatic juice a day
- Acini Cells secrete enzymes (propeptidases, amylase, lipase, (deoxy)ribonuclease) secreted through ducts
- ENDOCRINE -
- Islets of Langerhan secrete Glucagon (alpha cells) and Insulin (beta cells) which are secreted directly into blood
What is the function of propeptidases?
- digest proteins
- trypsinogen converted into TRYPSIN which:
- converters CHYMOTRYPSINOGEN into TRYPSINOGEN
- converters PROCARBOXYPEPTIDE into CARBOXYPEPTIDE
Both of these substances break down amino acids
What is the function of amylase?
Digests carbohydrates
What is the function of lipase?
Digestion of fats
What is the function of glucagon?
Increases blood glucose levels
What is the function of insulin?
Decreases blood glucose levels
What is the structure and function of the small intestine?
3 parts - duodenum, jejunum and ileum
- modified to increase surface area for better absorption (villi, microvilli)
- MECHANICAL DIGESTION - acid chyme mixed with pancreatic juice, bile and intestinal juice. Carbs, fats and proteins broken down
Describe the peritoneum
The largest serious membrane in the body!
- double layered and covers the abdominal and pelvic cavities
- has a rich blood supply of blood and lymph
- a physical barrier to local spread of infection
TWO LAYERS
- parietal - lines abdominal wall
- visceral - covers the organs
Explain the digestion of proteins
- Trypsinogen and Chymotrypsinogen activated by enterokinase and converted into trypsin and chymotrypsin
- These enzymes convert polypeptides into tripeptides and dipeptides into amino acids
Explain the digestion of carbohydrates
Pancreatic amylase converts all digestible polysaccharides (starches) not acted upon by salivary amylase to disaccharides
Explain the digestion of fats
Lipase converts fats to fatty acids and glycerol. Bile salts emulsify fats and reduce the size of globules increasing their surface area and making digestion easier!
What is the function of the large intestines?
Absorption of water and electrolytes.
Storage of undigested materials.
Contain goblet cells for mucous secretion!
What do goblet cells secrete?
Mucous
What does cholesystokinin (CCK) do?
STIMULATES:
- Pancreatic acini cells to secrete enzymes.
- The Gall bladder to release bile
- The sphincter of Oddi to relax
Also decreases gastric motility and secretion
What does Secretin do?
Stimulates the pancreatic duct cells to secrete water and sodium bicarbonate.
Also stimulates the liver to secrete bile.
Decreases gastric motility and secretions
How are lipids transported?
Transported as lipoprotein droplets (LD’s). If they are high density it means there is more protein and less fat!
- VLDLs (very low density) - transport triglycerides and cholesterol from liver to adipocytes to be stored (very bad for you)
- LDL’s (low density) - transport cholesterol to tissues (bad for you)
- HDL’s (high density) - remove cholesterol and return it to liver for elimination! (Good for you)
What substance is secreted by pancreatic alpha cells?
Glucagon
What substance is secreted by pancreatic beta cells?
Insulin
What is mechanical digestion?
Chewing, churning and swallowing
What is chemical digestion?
Digestion by enzymes, water, salts, buffers, mucous, bile and hormones
What does trypsin?
- activated pro-peptidases in duodenum and breaks down proteins
Proteins are acted upon in the stomach by:
Pepsin
Starch digestion in begins in the mouth when _____ is ducted in by the salivary glands
Salivary amylase
The substance that activates enzymes in the stomach and in the duodenum:
Trypsin (hormonal stimulus)
A non-enzyme substance that causes fat to be dispersed into smaller globules is:
Bile
The small intestine is protected from the corrosive action of acidic chyme by _________, which is ducted in by the pancreas
Bicarbonate-rich fluid
