A & P - digestive system Flashcards
what are the functions of the digestive system?
to provide energy
to build new tissue
what is the structure of the digestive system?
a long muscular tube from mouth to anus with modifications in various regions
what are the accessory organs of the digestive system?
salivary glands, liver and pancreas
what is the central upper abdominal region called?
epigastrium
what is the central lower abdominal region called?
hypogastrium or suprapubic
what is the peritoneum?
a double layer of serous membrane which covers the abdominal and pelvic cavities
what is the position of the parietal peritoneum?
it lines the body wall
what is the position of visceral peritoneum?
it covers the organs
What is the position of the peritoneal cavity?
it lies between the parietal and visceral peritoneum, it contains only serous fluid
The intraperitoneal organs are fully covered by the peritoneum, which organs are these?
stomach
part of small intestines
The retropertineal organs are partially covered by peritoneum, what are the organs and which position are they in?
pancreas and part of duodenum
pushed against posterior abdominal wall
What is the mesentery?
double layer of visceral peritoneum which attaches organs to body
What is the Omentum?
double layer of visceral peritoneum which attaches one organ to another
Name the 4 basic layers of the gastrointestinal tract
mucosa
submucosa
muscularis externa
serosa or adventia
where is the mucosa found in the GI tract?
forms lining of tract
name the 3 layers of the mucosa
epithelium
lamina propria
muscularis mucosa
what is the function of the epithelium of the mucosa in the GI tract?
protective
secretive
absorptive
what is the structure of the lamina propria of the mucosa in the GI tract?
connective tissue containing vessels, glands and lymphoid tissue
what is the structure of the muscularis mucosa of the mucosa of the GI tract?
smooth muscle
inner-circular
outer-longitudinal
what is the structure of the submucosa?
dense irregular connective tissue
what is the function of the submucosa?
supports mucosa
provides vascular, lymphatic and nerve (submucosal plexus) supply
what is the structure of the muscularis externa?
smooth muscle
inner- circular
outer - longitudinal
what is the function of the muscularis externa?
GI movements (peristalsis and segmentation)
what lies between the circular and longitudinal layers of smooth muscle in the muscularis externa?
myenteric plexus
what is the serous?
serous membrane that covers structures in the peritoneal cavity
name the 3 branches of the abdominal aorta that supply the GI tract
celiac trunk
superior mesenteric artery
inferior mesenteric artery
which system allows the blood from the stomach, pancreas, small and large intestine drain into the liver/
hepatic portal system
what is the function of the liver?
processes nutrients and secretes bile
what is the action of the autonomic nervous system on the GI tract?
causes long reflexes- large scale peristalsis etc.
which nerves control autonomic nervous system responses to the GI tract?
Vagus and Glossopharyngeal
where are most postganglionic nerves located?
enteric nervous system (submucosal and myenteric plexuses)
what action does the enteric nervous system have on the GI tract?
short reflexes - local peristalsis and glandular secretions
which glands control digestive function?
endocrine glands
what are the functional processes of the digestive system?
motility digestion secretion absorption protection
name 3 types of mechanical digestion
chewing
churning
segmentation
name 4 types of propulsion
swallowing
peristalsis
mass movement
elimination of waste
why does food need to be broken down by mechanical digestion?
move easily along tract
increase surface area to aid chemical digestion
what is the function of the temporomandibular joint and muscles?
aids the action of the teeth
what is the function of the salivery glands?
to produce saliva which begins chemical digestion and moistens bolus
what is segmentation?
cycles of contraction which fragment bolus and mix with digestive juices
what is peristalsis?
waves of muscle contraction which move bolus along
what are mass movements?
powerful peristalsis contractions
what stimulates the defecation reflex?
faeces in rectum
which sphincter needs conscious effort to relax?
external sphincter
what is chemical digestion?
breakdown of food into small fragments allowing absorption
what are carbohydrates broken down into during chemical digestion?
simple sugars
what are proteins broken down into during chemical digestion?
amino acids
what are lipids broken down into during chemical digestion?
fatty acids and monoglycerides
where are carbohydrates broken down?
mouth
small intestine
where are proteins broken down?
stomach
small intestine
where are lipids broken down?
mouth
small intestine
name some secretions secreted into the GI tract
water, enzymes, hormones
name 2 exocrine glands of the GI tract
salivary glands
pancreas
what do endocrine glands secrete?
hormones
what is absorption in the GI tract?
passage of substances across digestive epithelium to blood or lymph
Where does absorption occur in the GI tract?
stomach
small intestine
large intestine
what does the GI tract protect itself against?
acids
mechanical trauma
bacteria
what is the action of salivary amylase?
starts digestion of carbohydrates in the mouth
what is the action of lingual lipase?
starts digestion of lipids in the mouth
how much saliva is produced per day?
1 - 1.5 litres
the salivary glands produce serous fluid, what is its function?
wash oral cavity
what produces mucin?
the salivary glands, for lubrication
why do the salivary glands produce lysozyme?
it has antibacterial properties
how long is the oesophagus?
25cm long
where do the oesophagus go from and to?
pharynx to stomach
what is the oesophagus lined with?
stratified squamous epithelium
describe the different muscle types of the oesophagus
upper third - skeletal
middle third - mixed
lower third - smooth
Which nervous system innervates the oesophagus?
autonomic nervous system
which region of the abdomen is the stomach located?
epigastrium
what are the functions of the stomach?
storage mechanical/chemical digestion protection (kills microorganisms) absorption (alcohol/ aspirin) production of intrinsic factors
Describe the structure of the muscles of the stomach - inner, middle and outer
inner - oblique
middle - circular
outer - longitudinal
what is the function of rugae in the stomach?
increase surface area
what is the function of the mucous cell and neck mucous cell in the gastric pit?
secrete mucus
what is the function of the parietal cell in the gastric gland?
secrete hydrochloric acid and intrinsic factors
what do the chief cells in the gastric gland secrete?
pepsinogen
what do the enteroendocrine cells in the gastric gland secrete?
gastrin
how much gastric juice is produced daily?
1.5 - 2 litres
what activates the secretion of gastric juice?
low pH
gastrin
histamine
ACh
what is the function of hydrochloric acid in the stomach?
kill microbes
breakdown connective tissue (meat) and cell walls (plant)
activates pepsinogen to covert to pepsin
what is the function of pepsin?
starts protein digestion
what does gastrin stimulate?
secretion of pepsinogen and HCL
contraction of gastric wall
what is the function of intrinsic factors in gastric juice?
aids vitamin B12 absorption
what initiates the cephalic phase of gastric activity?
sight, smell, taste of food
what initiates the gastric phase of gastric activity?
food in stomach
what stimulates gastric juice production in the gastric phase?
gastrin
what initiates the intestinal phase of gastric activity?
partially digested food in duodenum - slows down gastric juice production and motility
describe the position of the pancreas
retroperitoneal
sits in curve of duodenum- posterior to stomach
name 3 parts of pancreas
head, tail ,body
name the sphincter where the pancreatic duct opens into the duodenum
sphincter of Oddi
how much pancreatic juice is secreted daily?
1.5 litres
what do the acini cells secrete?
enzymes
name the types of enzymes the acini cells produce
propeptides - digest protein
amylase - digests carbhydrates
lipase - digests fats
ribonuclease and deoxyribonulease - digest RNA and DNA
name the 3 propeptides enzymes that the acini cells secrete
trysinogen
chymotrysinogen
procarboxypeptidase
where are acini cells found
pancreas
what do duct cells in the pancreas secrete?
water
sodium bicarbonate
name the endocrine cells of the pancreas
Islets of Langerhans
what do the Islets of Langerhans produce?
alpha cells - glucagon
beta cells - insulin
describe the position of the liver in the abdominal cavity
right hypochodrium and epigastrium
what is the weight of the liver?
1.5 kg
name the 4 lobes of the liver
right
left
caudate
quadate
what is the function of the liver in relation to the digestive system?
bile production
what are the dimensions of the gall bladder?
8cm long by 4cm wide
what is the function of the gall bladder?
stores and concentrates bile
how much bile can the gall bladder hold?
40-70ml
what adaption does the gall bladder have which helps it to expand?
rugae
how long is the small intestine?
6 metres
mane the 3 modifications that the small intestine uses to increase surface area?
pilcae circulares
villi
microvilli (brush border)
what are the functions of the small intestines?
absorption
mechanical digestion
chemical digestion
what leads to the secretion of CCK (cholecystokinin) in duodenum?
presence of fat and proteins
describe the actions of CCK in chemical digestion
pancreatic acini cells - enzymes released
gall bladder - bile released
sphincter of Oddi - relaxes
stomach - reduced gastric motility and secretions
describe the actions of secretin in chemical digestion
pancreatic ducts - water and sodium bicarbonate released
liver- bile secreted
Stomach - reduced gastric motility and secreation
what reduces gastric motility and secretions in the stomach during chemical digestion?
CCK and Secretin
what converts trysinogen to trypsin during protein digestion?
enterokinase (located on brush border in duodenum)
what does trypsin activate?
other propeptides
what does the propeptide Chymotrysinogen convert to?
trypsinogen
what does the propeptide Procarboxypeptide convert to?
carboxypeptidase
what breaks down proteins into amino acids?
activated peptidases (such as trypsinogen)
what breaks down carbohydrates?
pancreatic amylase
what does pancreatic amylase break carbohydrates into?
disaccharides
trisaccharides
what coverts disaccharides and trisaccharides into monosaccharides?
brush border enzymes
what coverts maltose?
maltase
what coverts lactose?
lactase
what converts sucrose?
surase
how emulsifies large lipid droplets to small?
bile
what does pancreatic lipase break triglycerides down into during fat digestion?
free fatty acids
glycerol
what is formed when free fatty acids and glycerol interact with bile salts?
micelles
how do micelles enter intestinal cells?
diffusion
what are chylomicrons?
triglycerides formed from the re-synthesis of free fatty acids and glycerol
how are chylomicrons secreted into interstitial fluid?
exocytosis and diffusion into lacteals
describe the dimensions of the large intestine
1.5m long x 7.5cm diameter
name 2 functions of the large intestine
absorption of water and electrolytes
storage of undigested materials
what is the taenia coli of the large intestine?
longitudinal smooth muscle that forms haustra
what are the haustra of the large intestine?
small pouches caused by sacculation
what are epiploic appendages of the large intestine?
small pouches of fat
what are the crypts of the large intestine?
glands in lining
what are goblet cells?
cells which produce lots of mucus
what is the function of bacterial flora in the large intestine?
ferment undigested carbohydrate
synthesis vitamins B & K
what is the daily amount (of fluid and food) ingested and secreted into the body?
9200ml
what is the daily amount (of fluid and food)absorbed into the blood?
9050ml
what is the total amount (of fluid and food) which we excrete daily?
150ml
what are essential nutrients?
nutrients which can only be found in diet
what are macronutrients?
water, carbs, protein, fats - needed in large amounts
what are micronutrients?
vitamins and minerals - small amounts needed
why do we need nutrients?
growth and repair
name 3 types of carbohydrate
monosaccharides, disaccharides, polysaccharides
name 3 monosaccharides
glucose, galactose, fructose
name 3 disaccharides
sucrose, lactose, maltose
name 3 polysaccharides
starch, glycogen, cellulose - complex carbs
what do all carbohydrates generate?
glucose
name 3 functions of carbohydrates
convert to energy
provide energy stores
form structural components of other molecules eg. glycoprotiens
In what form are carbohydrates stored?
glycogen
what is fibre?
animal or plant carbohydrate that can’t be digested
what are the functions of fibre?
absorb water from intestines, soften stools
provide bulk - increase transit time
what is our daily requirement of fibre?
24g
what is our daily requirement of carbohydrate?
230g
what are the functions of proteins?
formation of: skeletal muscle hormones enzymes cell membrane receptors collagen haemoglobin
what is protein broken down to?
amino acids
what do proteins synthesis?
new proteins - transamination in liver
how many amino acids are there?
20
how many amino acids can’t be synthesised by body?
8
give some examples of amino acids
leucine phenylalanine glutamine lysine tyrosine methionine
what is our daily requirement of protein?
45-60g
which protein source plant or animal contains complete proteins and all essential amino acids
animal
what % of the body is made up of lipids?
men 15%
women 25%
what is the daily requirement of lipids?
70g/ only 20g should be saturated
what are lipids the precursor of?
steroids
bile salts
vit D
prostaglandins
Are lipids higher or lower in energy than sugars?
2 x higher
name 2 uses of lipids
absorption of fat-soluble vitamins
plasma membrane and myelin production
how are lipids transported in the blood?
as lipoproteins
what are lipids the core of?
cholesterol and triglycerides
what are lipids the outer coating of?
proteins and phosolipids
name 3 types of lipoproteins
high-density (HDLs)
low-density (LDLs)
very low-density (VLDLs)
what is the function of chylomicrons?
to transport triglycerides and cholesterol from small intestine to liver
what is the function of VLDLs?
transport triglycerides and cholesterol from liver to adipocytes
what is the function of LDLs?
transport cholesterol to tissue
what is the function of HDLs
empty shells made in liver which collect cholesterol dn return to liver for excretion - these are the best forms of lipoprotein
name 4 vitamins which the body can store
A, D, E, K - they are fat soluble so are stored in fat
name 2 vitamins which the body can’t store
B and C - they are water soluble so can’t be stored
recommended sodium intake?
6g per day but only need 2g
name some examples of minerals
calcium, phosphorus, iron, magnesium, manganese, chlorine, folate
name 5 minerals required during pregnancy
calcium. folate, zinc, iron, iodine
how many servings of carbohydrate is needed daily?
6-11
what is metabolism?
chemical and physical reactions that occur in body to ensure growth and functioning
what is anabolism?
Building up - small molecules join to form complex structures (uses energy)
what is catabolism?
breaking down - large molecules to small ones (releases energy)
how many kilojoules is in 1 kilocalorie?
4.184
what is a kilocalorie?
heat required to heat 1 litre of water by 1 degree (c)
what is metabolic rate?
rate of energy released from cells
what is basal metabolic rate?
energy release required to support vital organs at rest
during carbohydrate anabolism what is glucose converted to?
glycogen or triglycerides for storage
during carbohydrate catabolism what is glucose used to form?
ATP by glycolysis or the TCA cycle
Does glycolysis require oxygen?
No
what happens to glucose during glycolysis?
it splits into 2 pyruvic acid - producing 2 ATP
what happens to pyruvate if there is no oxygen present?
lactic acid is formed - result only 2 ATP
what happens to pyruvate if there is oxygen present?
pyruvate passes to mitochorion where it is converted to acetyl co enzyme A, it then enters TCA cycle and electron transport chain producing 36 ATP.
add this to 2 ATP formed in glycolysis and total of 38 ATP are formed for 1 glucose molecule
what are formed during protein anabolism?
new proteins made from amino acids
what are formed during lipid anabolism?
fatty acids and glycerol
triglycerides during lipogensis from amino acids anf glucose
name the 2 metabolic states
absorptive
post -absorptive
what is the purpose of the absorptive metabolic state?
mainly anabolic processes build up stores of energy
what is the purpose of the post absorptive metabolic state?
mainly catabolic process with breaks down stores for energy
why is blood glucose homeostasis important?
maintains blood glucose levels
what is the normal range of blood glucose?
- 5-8 mmol/L
3. 5-5.5 mmol/L fasting
what is glycogenesis?
creation of glycogen from glucose
what is glycogenolysis?
breakdown of glycogen into glucose
what is gluconeogenesis?
creation of new glucose from amino acids
is blood glucose high or low during absorptive state?
high
what does insulin do? and where is it secreted?
lower blood glucose - produced in the beta cells of pancreas
how does insulin lower blood glucose? (4)
increases entry of glucose into cells
stimulates glycogenesis
stimulates protein and fat synthesis
inhibits gluconeogenesis
how is blood glucose level maintained?
secretion of glucagon, adrenaline and glucocorticoids
where is glucagon secreted from?
alpha cells in pancreas
what does glucagon stimulate
glycogenolysis, gluconeogenesis and lipolysis
when are ketones produced?
when liver breaks down fats and proteins
how are ketones produced?
too much acetyl CoA to enter TCA cycle so acetyl CoA converts to ketone bodies
which cells need ketone bodies
heart and kidneys
what is ketoacidosis
too many ketones