MOD F TECH 38 Digestive System Flashcards
Digestive system
Definition
The organ system including the mouth, teeth, tongue, oesophagus, stomach, intestines and various glands that functions to ingest, digest and absorb nutrients
Food Groups
The three basic food groups are :-
•
- Carbohydrates
- Fats
- Proteins
Digestive Process
•Ingestion
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•Digestion
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•Absorption
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•Elimination
The Mouth
•Membranes produce mucus
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•There are also, three pairs of glands which produce up to 1500ml per day, of a complex substance called saliva
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•Saliva consists of :- Water, Mineral salts, mucus, immunoglobulins, blood clotting factors and the salivary enzymes
Tongue
Is a muscular organ which is attached to the hyoid bone and the mandible.
Functions :-
- Organ of taste
- Assists in mastication
- Assists in swallowing
Assists in speech
The Pharynx
The Pharynx :-
•The bolus of food is pushed into the pharynx by the tongue [“pharynx” essentially a muscular tube]
Epiglottis
The Epiglottis :-
- Is superior to the larynx and the junction of the oesophagus
- On swallowing, the epiglottis blocks the larynx, to allow food to go down the oesophagus without affecting the airway
The Oesophagus
•A soft muscular tube [flat] 25 to 30cm long
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•Runs down the gap in the “C” shaped rings of the cartilage surrounding the trachea and passes through the diaphragm at the level of the 10th thoracic vertebra to become the stomach
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•The oesophagus, moves the bolus of food towards the stomach by “Peristalsis”
The Stomach
•The stomach is the most dilated part of the digestive system, and it can hold up to 1500ml in the adult
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•The upper opening of the stomach is called the cardiac or lower oesophageal sphincter
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•The lower opening of the stomach is called the pyloric sphincter
Position
The Stomach
The fundus of the stomach lies in the left upper quadrant of the abdomen just inferior to the diaphragm
•Food is mixed with gastric juices which contain hydrochloric acid and an enzyme that begins the digestion of food
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•A lining of mucus prevents the walls of the stomach being digested by the enzyme
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•The function of the stomach is to churn up the food into a milky substance called “chyme” by mixing it with gastric juices
Gastric Juice
Functions of gastric juices
Secreted by special glands in the mucosa and consists of :-
•
- Water
- Mucus
- Hydrochloric acid
- Enzymes
- Gives acid reaction required by the enzymes
- Kills bacteria
- Stops the action of Amylase (enzyme in saliva which breaks down carbohydrates (starch) into simple sugars)
- After 2-6 hours the chyme is passed through the pyloric sphincter into the duodenum
The small intestine
•Is continuous with the stomach at the pyloric sphincter and leads into the large intestine
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- It is a little over six metres long and lies in the abdominal cavity surrounded by the large intestine
- In the small intestine the chemical digestion of food is completed and most of the absorption of nutrient materials takes place
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•The small intestine is described in three parts, which are continuous with each other
Duodenum
•Approx. 25cm long, it curves around the head of the pancreas.
•
•At its midpoint there
is an opening –common
to the pancreatic duct
and the common bile duct
•
•The bile, pancreatic and intestinal juices complete the conversion of the chyme into fats, amino acids and carbohydrates
Jejunum and Ileum
•The jejunum is the middle part of the small intestine and is about two metres long. It’s continuous with the….
•
- Ileum or terminal part, which is about three metres long
- Ends at the ileocaecal valve which controls the flow of material from the ileum to the large intestine and prevents regurgitation
Jejunum and Ileum
Large intestine “Colon
•The large intestine is about 1.5 metres long, and begins at the “caecum” in the right iliac fossa and terminates at the rectum and anal canal deep in the pelvis
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•It forms an arch around the coiled up small intestine
Functions of Large Intestine
•Absorption
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•Microbial activity
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•Mass movement
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•Defaecation
Accessory Organs
•The liver is the largest gland in the body and can weigh up to 2.3kg in the adult, and is described as having two lobes.
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•Following absorption in the small intestine the nutrient rich blood passes via the Portal vein to the liver
Liver
liver
Pancreas
•The pancreas is situated posterior to the stomach and anterior to the abdominal aorta and inferior vena cava
•
- It has two main functions………
- Production of pancreatic juice which is secreted into the duodenum via the pancreatic duct
•
•Production of insulin :- Insulin is a hormone produced by specialised cells in the pancreas called the “Islets of Langerhans”
Peritoneum
•A serous membrane which lines the abdomen and covers the abdominal organs
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- It prevents friction as the organs move against each other and helps to keep them in position
- It also carries and supports blood vessels within the abdominal cavity
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•It is richly supplied with blood and lymph vessels and contains a considerable number of lymph nodes
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•Has the ability to isolate an area of slowly developing inflammation, such as chronic appendicitis, preventing the spread of infection to the rest of the peritoneal cavity
Peritoneal Abdomen
Organs covered by the peritoneal lining
- Spleen
- Liver
- Stomach
- Gall bladder
- Bowel
Spleen
- Lies in the left hypochondrial region of the abdominal cavity, between fundus of the stomach and the diaphragm
- Size varies but usually approx. 12cm long, 7cm wide and 2.5cm thick
- Weighs approx. 200g
Functions of the Spleen
- Produce new leucocytes (white blood cells) and lymphocytes
- Store erythrocytes (red blood cells)
- Destroy old red blood cells
Kidneys
Kidney functions
•Filter blood to remove waste products such as urea
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•Regulate water and salt balance
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•Excrete urine
Ureters, Bladder and Urethra
- Ureters 25cm -30cm long tubes pass from kidneys to the bladder
- Bladder is a muscular reservoir bag that holds 300ml urine when full, but can be distended to hold more
- Urethra is the canal from the bladder to the outside of the body
The bladder lies in the pelvic cavity but rises into the abdomen when full
Female reproductive organs
The nine regions of the abdominal area
