Digestive system Flashcards
Function of digestive system
Alter ingested food
Form that can be absorbed by bloodstream
2 main areas of digestive system
Alimentary canal = hollow tube where food travels
Accessory digestive organs = structures which assist with digestive process
4 processes of digestive system
Ingestion
Digestion
Absorption
Excretion
Ingestion
Taking food into body
Digestion
Breaking down food/ components parts
Stomach & small intestine
Absorption
Small & large intestine
Uptake of nutrients in bloodstream
Excretion
Removal
Indigestible material
Faeces
Alimentary canal
Muscular tubular structure
Mouth to Anus
Areas of alimentary canal (8)
Oral cavity
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine
Rectum
Anus
Lumen
Hollow centre of gut
Structure of the gut (inside to outside) 5
Lumen
Mucosa ( with Muscularis mucosae inside)
Submucosa
Muscularis
Serosa
What is found in submucosa?
Blood vessels
Nerves
Connective tissue
Lymphatic vessels
What part of the gut moves food via peristalsis?
Muscularis layer
Function of serosa
Produce fluid - lubrication
Functions of oral cavity (4)
Pick food up
Boluses
Lubricate (saliva and mucus)
Digest carbs with amylase (omnivores/ herbivores)
Functions of tongue (6)
Compress on hard palate + move back to pharynx
Change shape to ladle to drink
Tastebuds
Heat loss mechanism
Vocalisation
Grooming
Structure of tongue (5)
Muscular structure
Attached to floor of mouth by frenulum
Skeleteal - volunteer muscle
Taste buds - info to brain
Has hyoid bone at its root
Structure and function of incisors
Chisel shaped & Rostral
Grasp prey & nibble on vegetation
Structure and function of canines
Pointed with Sharp apex & Wide base
Pierce/ hold onto prey
Structure and function of premolar & molar
Straight side, Wide flattened surfaces
Cusps on surfaces (rough)
Crush or grind
Carnassials
Carnivores only
Laterally flattened
Shearing
6 openings of pharynx
Oral cavity
Oesophagus
Naso-pharynx
Larynx/ trachea
2 eustachian tubes
Main function of pharynx
Convey food from mouth to oesophagus - deglutition
Stages of deglutition/swallowing (5)
- Bolus - passed to back of mouth
- Pharyngeal muscles
Cricopharyngeal sphincter
to oesophagus - Closes: epiglottis
+ naso-pharynx & eustachian tubes - Peristalsis to Oesophagus
- Epiglottis falls open again - air to trachea
Oesophagus - location and function (4)
Muscular tube - takes food from pharynx to stomach
Function=transport
Dorsal, left of trachea
When passes through thorax, runs through medastinum, dorsal to heart & between lungs
2 regions of oesophagus
Cervical
Thoracic
Proximal end of oesophagus
Inner circular muscler layer forms a sphincter called the cricopharyngeal sphincter
Distal end of oesophagus
No physical sphincter
but high pressure zone aka cardia/ cardiac sphincter
What is found in the mucous membrane of oesophagus?
Goblet cells which secrete mucus
4 regions of the stomach
Cardia
Fundus
Body
Pylorus
Cardia
Small region
Where oesophagus enters stomach
Fundus
Main reservoir
Can increase in size & maintain same intra-gastric pressure
Body of stomach
Intermediate section between storage and grinding section
Stores food
Pylorus (3)
Where food is ground (rhythmic segmentation) + mixed with gastric secretion
Move ingesta into duodenum
Controls rate that stomach empties into small intestine
Chyme
Food in stomach broken down into a liquid
Stomach: structure and location
C-shaped sac-like
Left side of abdomen
General function of stomach (3)
Reservoir
Break up food & mix with gastric juices
Begin digesting protein
Layers of the stomach (in to out) 4
Mucosa
Muscle layer
Submucosa
Serosa
Mucosa of stomach structure (2)
Mucous membrane
Gastric pits (deep folds)
What do parietal cells produce?
Hydrochloric acid
What do chief cells produce?
Pepsinogen
Where is the majority of acid?
Fundus
What is in the fundus? (2)
Majority of acid
Pepsinogen producing cells
What happens when stomach is full?
Mucosa is stretched smooth
What happens when stomach is empty?
Mucosa become wrinkled into folds aka rugae
What are rugae?
Folds found in mucosa layer of stomach
Functions of hydrochloric acid (3)
Proteins unfold to expose peptide bonds : allowing access to enzymes
Activates digestive enzymes
Inhibits growth of bacteria
Borders of the small intestine
Pylorus
to
Ileocaecocolic junction
Main functions of small intestine (2)
Digest
Absorb
3 sections of small intestine
Duodenum
Jejunum
Ileum
Function of elastic fibres in small intestine?
Cause the mucosa to be folded in the submucosa
Enterocytes?
Cells of the mucous membrane in the intestine
Where are enterocytes made?
At the base of each villus - aka Crypts of Lieberkühn
Contents of a villus (2)
Rich supply of capillaries
Single lymphatic vessel = lacteal
Function of capillaries in the villi?
Collect and transport absorbed nutrients
Go from enterocytes to hepatic portal vein
Function of lacteal?
Absorb and transport dietary fat from intestine
Secretions of digestion (5)
Bile
Lipase
Amylase
Bicarbonate
Trypsin
Where is bile produced?
Liver
Function of bile
Emulsify fat
Function of lipase
Digest fat
Function of amylase
Digest starch
Function of bicarbonate
Neutralises acidity of chyme
Function of trypsin
Digest proteins and peptides
Parts of the large intestines (4)
Caecum
Colon
Rectum
Anus
Caecum (4)
Blind ending tube at ileocaecocolic junction
Used as fermentation chamber in herbivores
Not used in carnivores
Vestigial in dogs and cats
Parts of the colon
Ascending
Transverse
Descending
Difference in structure between small intestine and large intestine? (5)
Similar basic structure
In large intestine:
No villi
Mucosa is flat
Crypts produce new epithelial and
goblet cells
Food is not broken down
Large intestine re-absorbs …
water and electrolytes
Function of rectum
Store faeces before defaecation
What do bacteria in colon produce?
B vitamins
Difference between inner sphincters and outer sphincters?
Inner - involuntary
Outer - voluntary
Contents of faeces (7)
Water
Fibre
Bacteria
Dead GI cells
Mucus
Bile pigment
Anal gland secretions
Accessory organs (4)
Salivary glands
Liver
Gall bladder
Pancreas
Contents of saliva
99% water
1% mucus
Functions of saliva (3)
Lubricate food
Thermoregulation
Breakdown of starch (via amylase) - herbivores & most omnivores
When is an increase of saliva noticed? (3)
Food is present
Animal is hurt
Animal is nauseous
Location of liver
Between diaphragm and stomach
What supplies oxygen to the liver?
Hepatic artery
What does the hepatic artery do?
Supply oxygen to liver
What is the function of the hepatic vein?
Carries blood back to the heart via vena cava
What is the function of the hepatic portal vein?
Brings nutrient rich blood from intestine
The liver receives…………% of the cardiac output
20
Of the cardiac output that the liver gets, what proportions are from hepatic artery and hepatic portal vein?
30% comes via hepatic artery
70% comes from hepatic portal vein
What is the liver enclosed with?
Thin sheet of epithelial cells called the capsule
Structure of the liver?
Thousands of lobules muo of cords of liver cells aka hepatocytes
What shapes are the lobules in the liver?
Hexagonal
10 functions of the liver
- Metabolise carbs
- Metabolise proteins
- Metabolise fat
- Bile formation
- Destruction of old RBC
- Formation of new RBC
- Storage of vitamins & glycogen
- Storage of iron
- Production of heat for body
- Detoxification
Function of hepatic ducts?
Bile from liver to gall bladder
Function of bile duct?
Bile from gall bladder to duodenum during digestion
Function of bile?
Emulsify fat globules
Surface area for lipase
What is the pancreas closely associated with?
Stomach and duodenum
Where is the pancreas?
In the U bend of duodenum
What tissues compose the pancreas
Exocrine - produces digestive enzymes
Endocrine - produces hormones
Pancreas secretions (5)
Bicarbonate (not an enzyme)
Trypsinogen
Trypsin
Lipase
Amylase
Function of bicarbonate
Neutralise the acid found in chyme
Function of trypsinogen
Precursor to trypsin which is activated in the SI
Function of trypsin
Breaks down proteins and peptides into amino acids
Function of lipase
Converts fats into fatty acids and glycerol
Function of amylase
Breaks down starch into maltose
Structure of stomach wall
Lined by mucosa
Deep folds aka sugar
In gastric pits:
- goblet cells produce mucus (protect from enzymes)
- chief cells produce pepsinogen
- parietal cells produce hydrochloride acid
2 types of movement in stomach & purpose
Peristalsis
Rhythmic segmentation
2 structures that empty into first part of small intestine
Pancreatic duct
Common bile duct
3 properties of intestinal villi that makes absorption more efficient
Large surface area
Excellent blood supply form network of internal capillaries
Thin layer of cells lining their wall
Surface area is further increased by presence of microvilli on surface of epithelial cells lining the villi
2 structures in villi and purposes they have
Capillary network: absorb carbs and proteins and relay them to hepatic portal vein
Lacteal: absorb fat in form of chyle (product of fat digestion) and relay it to lymphatic system (specifically to cisterns Chyli)
