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Parts of the digestive system - Coggle Diagram
Parts of the digestive system
Mouth
Made up of teeth with specialized shapes that break down the food into smaller pieces, increasing the surface area available for chemical breakdown as well as facilitating swallowing
Kinds of teeth
Deciduous teeth
the first set of teeth that humans and other mammals develop. They eventually fall off and are replaced by permanent teeth, that begin to grow in throughout childhood.
Permanent
The second set of teeth mammals grow. These do not fall off.
Mastication
Movement of the mouth which enables teeth to crush and grind food.
The anticipation of food in the mouth triggers the release of saliva by the salivary glands
Salivary glands
A gland associated with the oral cavity that secretes substances that lubricate food and begin the process of chemical digestion
The salivary glands of the mouth
Parotid gland
Sublingual gland
Submandibular gland
Saliva
Fluid which begins the chemical digestion of food made up of mucus, buffers, antimicrobial agents, and amylase.
Mucus
Viscous mixture of water, salts, cells, and slippery glycoproteins.
lubricates food for easier swallowing, protects the gums against abrasion, and facilitates taste and smell.
Buffers
help prevent tooth decay by neutralizing acid
Amylase
Enzyme which breaks down starch and glycogen
Antimicrobial agents
protect against bacteria that enter the mouth with food.
The esophagus
A muscular tube that conducts food by peristalsis from the pharynx (throat) to the stomach
Alternating waves of contraction and relaxation in the smooth muscles lining the alimentary canal that push food along the canal.
It secretes mucus
Stomach
structure
Has an elastic wall and accordion-like folds called rugae.
Rugae is in the mucous membrane lining of the stomach. These folds are not permanent but are rather temporary structures that allow the stomach to expand and contract to store and digest food.
Mucosa lines the insides of organs and cavities throughout your body that are exposed to particles from the outside. The mucous membrane lubricates and protects these organs from abrasive particles and bodily fluids.
The interior surface of the stomach wall is highly folded and dotted with pits leading into tubular gastric glands
Gastric glands
Cells that secrete the components of gastric juice
Types
Parietal cells
Produce the components of hydrochloric acid
Mucus cells
Secrete mucus
Lubricates and protects the cells lining the stomach
Chief cells
Secrete pepsinogen
HCl converts pepsinogen to active pepsin by clipping off a small portion of the molecule called a masking sequence (a low pH structure) and exposing its active site.
an inactive form of the digestive enzyme pepsin
Functions
Store food
Enabled by the rugae.
Digest food; process it into a liquid suspension
Enabled by gastric juice
Gastric juice is a digestive fluid secreted by the stomach that is mixed with food in a churning action by the stomach.
The mixture of ingested food and gastric juice is called chyme.
Components
Hydrochloric acid
disrupts the extracellular matrix that binds cells together in meat and plant material.
The concentration of HCl is so high that the pH of gastric juice is about 2, acidic enough to dissolve iron nails (and to kill most bacteria).
This low pH denatures (unfolds) proteins in food, increasing exposure of their peptide bonds
Pepsin
An enzyme that begins the hydrolysis of proteins
Breaks peptide bonds, it cleaves proteins into smaller polypeptides and further exposes the contents of ingested tissues.
Can contract a disease called gastric ulcers which are lesions in the lining
Gastric ulcers are caused mainly by the bacterium Helicobacter pylori.
The liver
Function
Secretes bile
Bile is a mixture of substances that enables formation of fat droplets in water as an aid in the digestion and absorption of fats.
Insoluble in water, fats form large globules that cannot be attacked efficiently by digestive enzymes so they need bile for their breakdown.
fat digestion is facilitated by bile salts, which act as emulsifiers (detergents) that break apart fat and lipid globules.
Bile salts are both hydrophyllic and hydrophobic
Considering that the environment in which digestion takes place is hydrophilic, this part of the bile salts molecules accelerates the digestion process and prevents the re-aggregation of emulsified lipids.
fats are hydrophobic so they react with hydrophobic parts of bile salts so that they can be broken into smaller parts.
Process of the workings of bile
Lipids enter small intestine
Bile is secreted by the gallbladder and sent to the small intestine
The bile salts in the bile coat the fat droplets and keep them from coalescing. These coated fat droplets are called micelles.
Smaller droplets of fat are formed and lipase from the pancreas, an enzyme that breaks down lipids, attack the droplets, breaking them down into fatty acids and monoglycerides.
These small fat molecules go on to form part of the cell membrane
Stored in the gallbladder
Maintains blood glucose level
Stores glycogen
Detoxifies poisonous chemicals in the blood
Pigments released during red blood cell disassembly are incorporated into bile pigments, which are eliminated from the body with the feces.
A large internal organ in vertebrates
Gall bladder
An organ that stores bile secreted by the liver and releases it as needed into the small intestine.
Located within the liver
Gal stones
hardened deposits of bile that can form in your gallbladder
develop because of an imbalance in the chemical make-up of bile inside the gallbladder. In most cases the levels of cholesterol in bile become too high and the excess cholesterol forms into stones.
Gall stones may block common bile and pancreatic ducts
When the bile duct is blocked, it blocks bile from entering the small intestine which impedes the digestion of fats
When the pancreatic duct is blocked, it blocks pancreatic juices from reaching the duodenum, resulting in inadequate digestion.
Blockage of pancreatic duct may also implicate inflammation and pain in your pancreas and pancreatitis.
Pancreas
Exocrine functions
Its secretions aid in digestion
Secretes enzymes
some enzymes it secretes are proteases trypsin and chymotrypsin, which are produced in inactive forms.
In a chain reaction similar to that for pepsinogen, they are activated when safely located in the lumen of the duodenum.
Secreted through the pancreatic duct
Lipolytic enzymes like pancreatic lipase
Carbolytic enzymes like pancreatic amylase
Nucleolytic enzymes like nucleases
Secretes bicarbonate
neutralizes the acidity of chyme and acts as a buffer for chemical digestion in the small intestine.
Secreted through the pancreatic duct
Endocrine functions
The endocrine portion is ductless
Functions in homeostasis
Secretes the hormones insulin and glucagon into the blood
When you eat a carbohydrate-rich meal and blood glucose increases, the pancreatic islets secrete insulin and consequently glycogen is formed in the liver and fat in adipose tissue.
When you fast or exercise and blood glucose is decreased, glucagon is secreted. Consequently, glycogen and fat are broken down.
Small intestine
Longest section of the alimentary canal
So named because of it small diameter relative to the large intestine
The principle site of the enzymatic hydrolysis of food macromolecules (chemical digestion) and the absorption of nutrients
Its large absorptive surface area is increased by villi, and microvilli.
Villi
finger-like projections in the inner surface/lumen of the small intestine
Microvilli
Finger-like microscopic projections in each epithelial cell within the villi.
Secretions
Proteases
Carbhydrases
Lipases
Nucleases
Mucus
Absorption process of proteins and carbohydrates
Pass the epithelial cell layer and enter the cell through active transport
Exit the epithelial cell into extracellular space through facilitated diffusion
Enter the capillary through diffusion
Absorption process of fats
Bile salts coat and emulsify fat gobules
The newly formed fat droplets are digested by lipases
The newly formed free fatty acids (monoglycerides) are coated with bile salts
the micelles gets rid of its bile salts and enter the epithelial cell layer as triglycerides
The triglycerides are covered in proteins forming chylomicrons
The chylomicrons are exocytosed from the epithelial cell layer
The chylomicrons enter the lacteal
Anatomy
Duodenum
where partially digested food, known as chyme, is mixed with digestive enzymes from the pancreas as well as from gland cells of the intestinal wall itself and bile from the liver and gallbladder.
The duodenum is the first and shortest part of the small intestine
The arrival of chyme in the duodenum triggers the release of secretin, which stimulates the pancreas to secrete bicarbonate.
Jejunem
This absorption of nutrients, including carbohydrates, proteins, fats, vitamins, and minerals, is a key function of the jejunum.
Where microvilli and villi are located
After food passes through the duodenum, it enters the jejunum.
Ileum
the final and longest segment of the small intestine
The primary functions of the ileum include further absorption of nutrients, especially vitamin B12, bile salts, and any remaining nutrients not absorbed in the earlier parts of the small intestine.
The ileum connects to the cecum, the first part of the large intestine (or colon), forming the ileocecal valve, which regulates the flow of material from the small intestine into the large intestine.
Lacteal
a tiny lymph vessel extending into the core of an intestinal villus and serving as the destination for absorbed chylomicrons
Large intestine
Movements
Peristalsis
Secretions
Feces
Composition of feces
Water
Undigested food
The undigested material in feces includes cellulose fiber. Although it provides no caloric value (energy) to humans, it helps move food along the alimentary canal.
Sloughed-off intestinal cells
Bacteria
Various organic compounds
Absorption
Water
Electrolytes
Vitamin K
Living in the large intestine is a rich flora
of mostly harmless bacteria
Bacteria produces vitamins
vitamin K
biotin
folic acid
Other B vitamins
Generates gases
Byproduct of bacterial metabolism
Methane
Hydrogen sulfide
It is called Escherichia coli
Parts
Rectum
The terminal portion of the large intestine, where the feces are stored prior to elimination
Anus
From this part feces is excreted
Colon
Ascending colon
Transverse colon
Descending colon
The largest section of the vertebrate large intestine; functions in water absorption and formation of feces.
Leads to the rectum and anus
Moves feces by peristalsis