Physiology and anatomy of the digestive system Flashcards
Digestive system definition?
The digestive system is made up of the alimentary tract or the gastrointestinal
tract (GI tract) and accessory organs, salivary glands, liver, pancreas, and
gallbladder
Series of hollow organs
Organs of the GI tract?
(the mouth, oesophagus, stomach, small intestine, large intestine, and anus).
Accessory organs?
salivary glands, liver, pancreas, and gallbladder are the solid organs of the digestive system.
Main functions of the digestive system?
Digestion
Secretion
Absorption
Motility
Start of the large intestine?
Colon
Where does the most water reabsorbed in the GIT?
Colon
Function of liver?
Sieve blood, toxins, nutrients etc
to make and secrete bile and to process and purify the blood containing newly absorbed nutrients that are coming from the small intestine.
The liver filters blood from the stomach and intestines, removing toxins, byproducts, and other harmful substances
Direction of motility in GIC?
Mouth to anus
Motility definition?
The ability of an organism to move independently,, using metabolic energy
What occurs n the small intestine?
Digestion then Absorption then secretion
Dumplings syndrome?
Coming form rapid increase osmolarity inside the GIT
Due to quick breakdown of macromolecules
Rapid absorption of blood inside GIT
Symptoms of sumpings syndrome?
Weakness
Dizziness
Vertigo
Tachycardia
Abnormal cramping
Self-limiting
Epigastric fullness
Digestion absorption?
the passage of the end products of digestion from the
gastrointestinal tract into the blood, and lymphatic vessels.
Absorption of this kind can take place either by diffusion or by active transport.
Role of the stomach in GIT?
Digestion of proteins; food stuffs reduced to semi-liquid from; storage; sterilisation
Role of the pancreas?
Digestion enzymes for digestion of fats, carbohydrates and proteins
The pancreas produces enzymes that break down food, including proteins, fats, carbohydrates, and acids. The pancreas also secretes bicarbonate to neutralize stomach acid.
Exocrine
Exocrine system?
Secreted through ducts
Gallbladder?
Stores and concentrates bile, ready for eating of fats
Bile salts?
Bile salts help with the digestion of fats. They also help the body absorb fat-soluble vitamins, like vitamins A, D, E, and K. Bile and bile salts are made in the liver and stored in the gallbladder between meals.
4 layers of the GIT?
Mucosa
Submucosa
Muscular externa
Serosa/adventitia (CT sheet; known as serosa in peritoneal cavity – adventitia if outside the peritoneal cavity)
Layers of the mucosa?
Epithelium
Lamina propria
Muscularis mucosae
What forms teh lining of the abdominal cavity?
The periosteum is serous membrane
Epithelium on the mouth, osesophagus and canal?
Stratified squamous
Epithelial lining of the stomach, small and large intestine?
Simple columnar
Role of the mucosa?
Synthesis and secretion of digestive enzymes, hormones and mucus
Absorbs products of digestion
Layers of muscularis externa?
- Two concentric thick layers of smooth muscle
Inner layer = circular muscle (constricts lumen)
Outer layer = longitudinal muscle (shortens tube)
Produce motility
Peristalsis and segmentation?
involuntary muscle movements in the digestive system that help move food and break it down for absorption
Peristalsis: move food along GI
Segmentation: mixes food with digestive juices, occurs in intestine
Nervous control of GI?
Parasympathetic = vagus
Sympathetic = splanchnic nerve
Effect of vagus nerve?
Parasympathetic
(except salivation facial (VII) and glossopharyngeal (IX))
Stimulatory
Increase secretion
increase motility
Effect of spanchnic nerve?
Sympathetic
Inhibitory (except salivation)
Decrease secretion
Decrease motility
Summary of Hepatic portal circulation?
The hepatic portal circulation is a specialized part of the circulatory system that directs blood from parts of the gastrointestinal (GI) tract and spleen to the liver.
It plays a key role in nutrient absorption, detoxification, and metabolic regulation.
How is chewing controlled?
1) voluntary
Somatic nerves —> skeletal muscles of mouth/jaw
2) reflex
Barorecpetor reflex
Pain reflex
Blood flow pathway of the hepatic portal circulation?
From GI tract and spleen: Blood from the stomach, intestines, spleen, and pancreas collects in veins known as the portal veins.
Hepatic Portal Vein: This portal vein carries nutrient-rich blood to the liver.
It is formed by the joining of the superior mesenteric vein (from the small and large intestines) and the splenic vein (from the spleen).
Function of hepatic portal circulation?
1) Nutrient Processing:
- After food is digested and absorbed in the intestines, nutrients (like glucose, amino acids, and fats) a
re carried to the liver. The liver processes these nutrients, stores some (like glycogen), and releases others (like glucose) into the bloodstream.
2) Detoxification:
- The liver filters toxins, drugs, and waste products from the blood before they enter general circulation.
3) Metabolism Regulation:
The liver helps regulate blood sugar levels (through glycogenesis and glycogenolysis), synthesizes proteins (e.g., albumin, clotting factors), and stores fat-soluble vitamins and minerals.
Livers role in hepatic portal circulation?
Once the blood reaches the liver, it is processed by liver cells (hepatocytes), which filter, store, and metabolize the absorbed substances.
The liver then sends blood to the heart via the hepatic veins, which drain into the inferior vena cava and return the blood to systemic circulation.
Clinical relevance of hepatic portal circulation?
Portal Hypertension: Increased pressure in the portal vein, often due to liver diseases like cirrhosis, can lead to varices (swollen veins) and other complications.
Nutrient Imbalance: Impaired hepatic portal circulation can disrupt nutrient processing, leading to malabsorption or nutrient deficiencies.
Components of saliva?
Water
Mucins
Alpha-amylase
Electrolytes
Lysozyme
Functions f the stomach?
- Temporary store of ingested material
- Dissolve food particles and initiate digestive process
- Control delivery of contents to small intestine
- Sterilise ingested material
- Produce intrinsic factor (Vitamin B12 absorption)
Role of B12?
Formation of myelin sheath
Formation of RBC
Where is b12 absorbed?
Bind intrinsic factor and absorbed in Ilium
IF is a glycoprotein that helps the body absorb vitamin B12 in the terminal ileum.
Pernicious anaemia?
Lack of B12, lack of intrinsic factor and lack of absorption
Happens gradually
Intrinsic factor?
IF is a glycoprotein that helps the body absorb vitamin B12 in the terminal ileum.
What cells the stomach produce HCL and if?
Parietal cells
What cells produce mucus?
Mucous neck cells
moa of orlistat?
Inhibit lipase, wont digest fats
