Gastrointestinal: Anatomy Flashcards
What are the 2 paths for GI regulation?
Neural and endocrine
How is food intake regulated? (2)
Is not based on homeostasis
Maximise absorption - whether nutrients needed or not
What are the 2 major parts of the GI system?
GI tract - organs joined to process food
Accessory glands - secrete fluids and enzymes
What does the GI system supply the body with? (3)
Water
electrolytes
Nutrients
How is the GI system controlled? (2)
Hormonal and nervous system
What is an autotroph?
Synthesise all essential organic nutrients from inorganic sources
What is a heterotroph?
Have limited synthetic abilities - require organic compounds in the form of food
What are the 8 essential amino acids?
Tryptophan Methionine Threonine Phenylalanine Valine Leucine Isoleucine Lysine
What are the 3 macro constituents?
Carbs
Proteins
Lipids
What are the 3 micro constituents?
Vitamins
Minerals
Water
What are the 3 properties of the gut tube?
Hollow tube
15ft long
Open to the outside world
What are the 4 basic processes of the gut tube?
Digestion
Absorption
Motility
Secretion
What is the anatomy of the GI tract? (6)
Oral cavity Oesophagus Stomach Small intestine Large intestine Rectum
What are the 4 layers of the digestive tract?
Mucosa - lining Submucosa - layer of connective tissue Muscular externa - smooth muscle fibres Serosa - outer layer of connective tissue (In to out)
What is the mucosa made up of? (3)
Mucous membrane
Lamina propria
Muscular mucosae
What is the role of the mucous membrane in the mucosa? (4)
Epithelial cells layer (enterocytes):
- absorptive
- exocrine
- goblet
- endocrine
What is the lamina propria? (2)
Connective tissue underlying mucous membrane
Blood vessels, nerves and lymphatics
What is the role of muscular mucosae? (3)
Thin layer of smooth muscle
Lots of folds
Promotes movements
What is the submucosa made up of? (2)
Connective tissue
Enteric nervous system
What is the role of connective tissue in the submucosa? (3)
Provide GI tract with elasticity and distensibility
Tolerate stretch
Contain larger blood and lymphatic vessels
What is the role of the enteric nervous system in the submucosa? (3)
Sensory, motor and inter neurone
Regulates GI functions
Output from enteric goes to effector cells
What is the makeup of the muscularis externa? (3)
Inner layer of circular muscle
Outer layer of longitudinal muscle
Contraction - regulates movement of the gut
What is the makeup of the serosa? (2)
Inner layer - fibrous tissue, structural support
Outer layer - epithelial tissue, secretions
Where is HCl secreted from?
Pits
What are the organs of the GI tract? (6)
Pharynx Oesophagus Small Intestine Colon Rectum Anus
What is the mouths role in digestion? (2)
Mastication is the start - chewing Saliva secretion (lubricant) and digests (amylase)
What is the oesophagus’ anatomy? (2)
Top 1/3 - skeletal muscle
Bottom 2/3 - smooth muscle
Describe the 3 stages of the swallowing reflex?
- Tongue pushes bolus against back of mouth, trigger
- Upper esophagus sphincter relaxes while epiglottis closes (keeps airways closed)
- Food moves downwards into oesophagus by peristaltic waves and gravity
What is the function of the stomach in digestion? (4)
> Stores food after it has been swallowed
Secretes gastric juice
releases food into intestine slowly
regulated by pyloric sphincter
What is the anatomy of the stomach? (4)
Fundus
Body
Antrum
Rugae (curls)
Why is the stomach acidic? (4)
Necessary for pepsinogen activation
Kills bacteria
Denatures proteins
Gastric mucosal barrier (bicarbonate and mucus layer)
What are gastric pits? (4)
Secrete enzymes
- pepsinogen (chief cells)
- Hydrogen ions (parietal cells)
- Gastrin (G cells)
- Mucus (neck cells)
What is the structure of the small intestine? (4)
Coiled, hollow
8-10ft long
Between stomach and large intestine
3 divisions: duodenum (top, excretes), jejunum (middle, absorbs), ileum (bottom, absorbs)
What is secreted into the duodenum? (2)
Pancreatic juice (digestive enzyme and bicarbonate) Bile (salts which aid fat digestion)
What is the anatomy of the small intestine wall? (4)
Villi
Blood vessels
Lacteal (absorption)
Microvilli
What are the crypts of Lieberkuhn?
Epithelial cells in crypts secrete bicarbonate
What is the role of the liver in absorption? (2)
Absorbed nutrients in the blood travel to liver before general circulation
Liver detoxifies
What is the blood supply to the liver? (2)
Hepatic portal vein from small intestine
Hepatic artery from aorta
What is the large intestine made up of? (4)
Cecum
Colon
Rectum
Ileocecal sphincters between ileum and colon
What are the functions of the large intestine? (3)
Concentrates wastes into faeces
Absorption of most water
Stores faeces until defecation
What are the 4 sections of the colon?
Ascending colon
Transverse
Descending
Sigmoid
What is the relationship between the rectum and the anus?
Colon empties into rectum, then faeces through anus
What are the 2 types of sphincters in the anus?
Internal anal sphincter - smooth muscle
External anal sphincter - skeletal muscle
Must relax both to poo
