digestive system Flashcards
functions
ingestion
secretion
mechanical processing
digestion
absorption
defeacation
ingestion
digestive tract via the oral cavity
An active process involving conscious choice and decision-making
secretion
non-specific defence against the corrosive effects of digestive acids and enzymes
water, acids, enzymes, buffers, and salts from the epithelium of the digestive tract and glandular organs into the digestive tract
mechanical processing
Physical breakdown of food into smaller particles that makes materials easier to propel along the digestive tract
Mixes the food with secretions and increases the surface area of the food,
digestion
Chemical breakdown of food into small organic fragments suitable for absorption by the digestive epithelium
absorption
The movement of organic molecules, electrolytes (inorganic ions), vitamins, and water across the digestive epithelium, into the interstitial fluid
defacation
Elimination of wastes, indigestible substances, bacteria, dead cells from the body.
4 layers of digestive tract
muscosa
submucosa
muscularis
serosa
mucosa
inner lining where The locations where absorption occurs,
moistened by glandular secretions
submucosa
Dense, irregular connective tissue beneath the mucosa
Has numerous blood vessels and lymphatic vessels
muscularis
Dominated by smooth muscle cells
The inner circular layer is essential for agitation and in the formation of valves
The outer longitudinal layers of muscle is essential for mechanical processing
serosa
Covers the muscularis externa along most portions of the digestive tract
oral cavity
lubrication by mixing with mucus and saliva
mechanical digestion through the actions of the teeth, tongue and palatal surfaces
-initiation of carbohydrate digestion by salivary amylase
- initiation of lipid digestion by lingual lipase
salivary glands
lysozyme: kills bacteria
- enzymes: salivary amylase and lingual lipase
Saliva:
- lubricates the food and helps combine materials in the mouth with the digestive enzymes
pharynx
passageway for solid food, liquid and air. Swallowing is the process that allows for a substance to pass from the mouth
oseophagus
hollow muscular tube, posterior to the trachea, that conveys solid food and liquids to the stomach.
peristalsis then into the stomach through an open lower oesophageal sphincter
liver
Metabolic regulation:
- modifies and stores excess glucose, amino acids, and fatty acids therefore stabilising blood glucose levels
Haematological regulation – synthesis and release of the plasma proteins, including albumin, transport proteins, clotting proteins, and complement proteins.
Bile production – bile salts break lipid droplets apart in a process called emulsification, which dramatically increases the surface area
gall bladder
stores and concentrates bile prior to its excretion into the small intestine
stomach
Parietal cells:
- secrete intrinsic factor – required for the absorption of vitamin B12 in the small intestine
secrete hydrochloric acid
Chief cells:
- secrete pepsinogen – becomes pepsin when activated by HCl, digests protein.
pancreas
ecause it secretes the hormones, insulin and glucagon into the bloodstream.
Exocrine – because it secretes pancreatic juice into the duodenum. Pancreatic juice contains:
- an alkaline solution containing bicarbonate
small intestine
Duodenum – first and shortest segment of small intestine, receives chyme from the stomach and digestive secretions from the pancreas and liver.
Jejunum – middle segment of small intestine, is the location where the most chemical digestion and nutrient absorption occurs.
illeum- final segment of small intestine that ends at the ileocecal valve which is a sphincter that controls the flow of material from the ileum into the cecum of the large intestine.
teeth
mastification
tearing apart your food
then the tongue will squash
mechanical digestion
mastification
mixing and churning
segmentation
peristalis
increases surface area of food
peristalis
Contraction of circular muscles
behind bolus
2. Contraction of longitudinal
muscles ahead of bolus
3. Contraction of circular muscle
layer forces bolus forward
contraction
contraction
contraction
longitudinal muscle
circular muscle
carbohydrates
Monosaccharides are the smallest carbohydrate. They can be absorbed and are water soluble
Disaccharides are two monosaccharides joined together. They are water soluble
Complex carbohydrates do not dissolve in water or other body fluids
function of protein
Structural proteins create a framework for the body
Contractile proteins bring about muscle contraction
Transport proteins transport substances in the blood
Form hormones for coordination and control of body processes
Provides pH buffering to prevent dangerous pH changes of body fluids
Control metabolic reactions.
Provide defense against pathogens e.g., antibodies
primary amino acid
the sequence of amino acids along the length of a single polypeptide. Peptide bonds are responsible for the primary structure of proteins.
secondary amino acids
the shape that results from the presence of hydrogen bonds between atoms at different parts of the polypeptide chain. Hydrogen bonding may create either an alpha helix or beta sheets.
tertiary amino acids
the complex coiling and folding that gives a protein its final 3D shape. Tertiary structure results primarily from hydrophobic, hydrophilic and disulphide bonds.
quarternary structure
he interaction between individual polypeptide chains to forma a protein complex.
lipids
Structural component e.g. plasma membrane
Energy source – provide twice as much energy as carbohydrates do, gram for gram but when in excess stores in fat deposits
Chemical messenger – to corrinate cellular activites
Insulation – fat deposits slow heat loss to the environment
Protection – fat deposits around delicate organs such as the kidneys provides a cushion that protects against bumps or jolts.
age to digestion
Epithelial stem cell division rate decreases – this results in the epithelium being more susceptible to damage by abrasion, acid and enzymes and can lead to peptic ulcers as tissue repair is less efficient with aging.
Smooth muscle tone decreases – this results in a decrease in general motility and weaker peristaltic contractions leading to constipation. Straining to eliminate compacted faecal matter stresses less resilient blood vessels causing haemorrhoids. Weakening of muscular sphincters can lead to oesophageal reflux and heartburn.
Cumulative damage from toxins (e.g. alcohol) can lead to a gradual loss of teeth due to dental cavities, liver cirrhosis, and cancer.
