6.1 Digestive System Flashcards
1
Q
what are the 2 major groups of organs which comprise the human digestive system?
A
- alimentary canal -> organs which food pass through
- accessory organs - aid digestion but don’t actually transfer food
2
Q
what does the oesophagus do and what is it? (2)
A
- hollow tube connect oral cavity to stomach
- food mixed with saliva and moves in a bolus via peristalsis action
3
Q
what is the stomach and how does it function? (2)
A
- temporary tank where food is mixed by churning and protein
- lined by gastric pits that release digestive juices (acidic environment pH-2)
4
Q
what is the small intestine and how does it function? (2)
A
- long, highly folded tube where usable food substances are absorbed
- consists of 3 parts (duodenum, jejunum and ileum)
5
Q
what is the large intestine and how does it function? (2)
A
- final section of alimentary canal, where water and dissolved minerals are absorbed
- consists of ascending/transverse/descending/sigmoidal colon as well as rectum
6
Q
what is the salivary gland and its function? (2)
A
- release saliva to moisten food and contains enzymes (starch breakdown)
- includes parotid gland, submandibular gland and sublingual gland
7
Q
what is the pancreas and its function? (2)
A
- produce a broad spectrum of enzymes that are released into the small intestine via duodenum
- secretes certain hormones (insulin/glucagon) regulates sugar conentrations
8
Q
what is the liver and its function? (2)
A
- takes raw material absorbed by the small intestine and uses them to make key chemicals
- includes detoxification, storage, metabolism, bile production and haemoglobin breakdown
9
Q
what is mechanical digestion? (3)
A
- food is initially broken down in mouth by grinding of teeth
- tongue pushes the food towards the back of the throat where it travels down oesophagus as a bolus
- epiglottis prevents the bolus from entering the trachea while the uvula prevents the bolus from entering the nasal cavity
10
Q
what is churning digestion? (3)
A
- stomach lining contains muscles which physically squeeze and mix the food with strong digestive juices
- food is digested within the stomach for several hours and turned into a creamy paste called chyme
- eventually chyme enters the small intestine where absorption will occur
11
Q
what is peristalisis? (3)
A
- peristalisis is the principal mechanism of movement in oesophagus although it also occurs in both stomach and gut
- continuous segments of longitudinal smooth muscles rhythmically contract and relax
- food is moved unidirectionally along the a causal direction
12
Q
what is segmentation? (3)
A
- segmentation involves the contraction and relaxation of non-adjacent segments of circular smooth muscle in intestines
- segmentation contractions move chyme in both directions, allowing for a greater mixing of food with digestive juices
- segmentation helps to physically digest food particles, its bidirectional propulsion of chyme can slow overall movement
13
Q
how do stomach acids work? (4)
A
- stomach contains gastric glands which release digestive acids to create a low pH environment
- the acidic environment function to denature proteins and other macromolecules aiding in overall digestion
- stomach epithelium contains a mucous membrane which prevents acids from damaging gastric lining
- pancreas alkaline compounds which neutralise the acids as they enter the intestine
14
Q
how does bile work? (3)
A
- liver produces (stored in gall bladder)
- bile contains bile salts which interact with fat globules and divide them into smaller droplets
- emulsification of fats increase SA for enzyme activity
15
Q
how are carbohydrates digested? (4)
A
- digested by amylase from salivary glands
- also secreted by pancreas
- enzyme for disaccharide hydrolysis are immobilised on epithelial lining of small interesting near channel proteins
- humans don’t possess an enzyme for digesting cellulose and it passes through the body
16
Q
how are proteins digested? (3)
A
- protein digested in stomach by protease (acidic pH)
- smaller polypeptide chains enter small intestines where they are broken down by endopeptidases released by pancreas
- endopeptidases work optimally in neutral environment in acid
17
Q
how are lipids broken down? (2)
A
- lipid breakdown occurs in intestines beginning emulsification of fat globules by bile from gall bladder
- smaller fat droplets are digested by lipases release from pancreas
18
Q
how are nucleic acids broken down?
A
- pancreas also release nucleases which digest nucleic acids (DNA/RNA) into smaller nucleosides
19
Q
what is the structure of the small intestine? (4)
A
- Serosa - protective outer covering composed of a layer of cells reinforces by fibrous connective tissue
- Muscle layer - outer layer of longitudinal; muscle (peristalsis) and inner layer of circular muscle (segmentation)
- Submucosa - composed of connective tissue separating the muscle layer form the innermost mucosa
- mucosa - highly folded inner layer which absorbed material through its surface epithelium from intestinal lumen
20
Q
what are the features of villi? (6)
A
- microvilli - ruffling of epithelial membrane increase SA
- rich blood supply - dense capillary network absorbed products
- single layer epithelium - minimises diffuses distance between lumen and blood
- lacteals - absorbs lipids from the intestine lymphatic system
- intestinal glands - exocrine pits release digestive juices
- membrane proteins - facilitated transport of digested material into epithelial cells
21
Q
what are structures of intestinal villi? (4)
A
- tight junction - occluding associations between the plasma membrane of two adjacent cells, creating an impermeable barrier
- microvilli - increase SA
- mitochondria - epithelial cells of intestinal villi will possess large numbers of mitochondria to provide ATP for active transport
- pinocytotic vesicles - pinocytosis is non-specific uptake of fluids and dissolves solutes
22
Q
what are the 4 different membrane transport mechanisms?
A
- secondary active transport
- facilitated diffusion
- osmosis
- simple diffusion
23
Q
what is secondary active transport?(2)
A
- transport protein coupkees the acrtive translocation of 1 molecule to the passive movement of another
- glucose and amino acids are co-transported across the epithelial membrane by the active translocation of sodium ions
24
Q
what is facilitated diffusion? (3)
A
- channel proteins help hydrophilic food molecules pass through the hydrophobic portions of the plasma membrane
- channel proteins are often situated near specific membrane-bound enzyme (creates localised conc grad)
- certain monosaccharides, vitamins and some minerals are transported by facilitated diffusion
25
Q
what is osmosis? (2)
A
- water molecules will diffuse across the membrane in response to the movement of ions and hydrophilic monomers
- absorption of water and dissolved ions occur in both small and large intestine
26
Q
what is simple diffusion? (2)
A
- hydrophobic materials freely pass through the hydrophobic portion of plasma membrane
- once absorbed, lipids will often pass into lacteals than being transported via blood
27
Q
how does endocytosis? (4)
A
- involves invagination of plasma membrane to create internal vesicle containing extracellular material
- requires breaking and reforming of phospholipid bilayer (energy-dependent)
- in intestine, vesicles form around fluid containing dissolves materials
- pinosytosis allows material to be ingested in mass (less time than shuttling via membrane proteins
28
Q
how is starch digested?
A
- initiated by salivary amylase in the mouth
- continued by pancreatic amylase in the intestines
29
Q
how does amylase work?
A
- amylase digests amylose into maltose subunits and digests amylopectin into branched chains called dextrin
- maltose and dextrin digested by enzymes in the epithelial lining of small intestine
- the hydrolysis of maltose/dextrin results in formation of glucose monomers
30
Q
what is the role of pancreas? (2)
A
- it produces the enzyme amylase which is released from exocrine glands into the intestinal tract
- produces the hormones insulin and glucagon which are released from endocrine glands into the blood
31
Q
what does insulin and glucagon do? (3)
A
- insulin and glucagon regulate concentration of glucose in bloodstream
- insulin lowers blood glucose levels by increasing glycogen synthesis and storage in the liver and adipose tissue
- glucagon increases blood glucose levels by limiting the synthesis and storage of glycogen by the liver and adipose tissue
