Digestive system
The process by which large complex nutrient molecules are broken down into simpler molecules capable of being used by the organism for food.
Digestion
Food can be broken down (digested) in two ways:
1. Physical Digestion
2. Chemical Digestion
This is where large pieces of food are broken down into smaller pieces of the same food. Mechanical (physical) digestion can be achieved through the following actions: Chewing, Tearing, Grinding, Mashing, And Mixing
Physical Digestion
This is where food is broken down into a different substance that can easily pass into the blood with the help of enzymes
Chemical Digestion
โข An ______ is a biological catalyst that speeds up chemical reactions
โข All chemical reactions that take place in living systems require the action of an ______
ENZYMES
________ break food down into smaller, more soluble substances which allows the food to be absorbed into the blood and become utilized by the body
Digestive enzymes
STAGES OF NUTRITION
1. ๐๐๐ฉ๐๐ฃ๐ (also called ๐๐ฃ๐๐๐จ๐ฉ๐๐ค๐ฃ)
2. ๐ฟ๐๐๐๐จ๐ฉ๐๐ค๐ฃ (Breakdown of ingested food)
3. ๐ผ๐๐จ๐ค๐ง๐ฅ๐ฉ๐๐ค๐ฃ (Passage of nutrients into the blood)and Metabolism (Production of cellular energy (๐ผ๐๐")
4. ๐๐ก๐๐ข๐๐ฃ๐๐ฉ๐๐ค๐ฃ of undigested food (also called "๐๐๐๐จ๐ฉ๐๐ค๐ฃ")
The Components of the Digestive System
- continuous coiled hollow tube from mouth to anus. It is a "tube within a tube".
1. Gastrointestinal (Gl) tract (๐ผ๐ก๐๐ข๐๐ฃ๐ฉ๐๐ง๐ฎ ๐๐๐ฃ๐๐ก)
Structures of digestive:
โข Mouth/ Oral Cavity
โข Pharynx
โข Esophagus
โข Stomach
โข intestines
Accessory structures of digestive:
โข Salivary glands
โข Liver
โข Gall bladder
โข Pancreas
The contents of the ๐๐ก๐๐ข๐๐ฃ๐ฉ๐๐ง๐ฎ ๐๐๐ฃ๐๐ก are pushed along by a rhythmic pulsations or alternating contraction of the muscles of the GI tract. This is known as _______.
peristalsis
- is a serous membrane lining the abdominal cavity.
Peritoneum
Two types or layers of peritoneum and a potential space between them are referenced:
1. parietal peritoneum
2. visceral peritoneum
3. peritoneal cavity
4. mesentery
The outer layer, called the ________, is attached to the abdominal wall and the pelvic walls
parietal peritoneum
The inner layer, the ________, is wrapped around the visceral organs , located inside the intraperitoneal space for protection . It is thinner than the parietal peritoneum.
visceral peritoneum
The potential space between these two layers is the __________; it is filled with a small amount (about 50 mL) of slippery serous fluid that allows the two layers to slide freely over each other.
peritoneal cavity
The term _______ is often used to refer to a double layer of visceral peritoneum. This is a peritoneum folded upon itself extending from the organ to the abdominal wall These are often blood vessels, nerves, and other structures between these layers. The space between these two layers is technically outside of the peritoneal sac, and thus not in the peritoneal cavity.
mesentery
- Extends from the lips to the orophaynx. Initial digestion of carbohydrates occurs here. It contains the teeth, tongue, palate, salivary glands and tonsils
MOUTH (Oral Cavity)
protect the anterior opening of your mouth
โขLips (labia)
โข form the lateral walls
Cheeks
โข forms the anterior roof
Hard palate
โข forms the posterior roof
Soft palate
โข fleshy projection of the soft palate
Uvula
โข space between lips externally and teeth and gums internally
Vestibule
โข area contained by the teeth
Oral cavity
โข attached at hyoid and styloid processes of the skull, and by the lingual ๐๐ง๐๐ฃ๐ช๐ก๐ช๐ข. It contains the receptor for taste.
Tongue
โข lymphoid tissue, part of body defense system
- Palatine tonsils
- Lingual tonsil
Tonsils
โข An adult human has _____ ๐ฉ๐๐๐ฉ๐,
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Regions of a Tooth
1. Crown
- Enamel
- Dentin
- Pulp
2. Neck
3. Root
exposed part of the tooth
crown
- most outer part; the strongest part of the tooth
Enamel
- the main body which is bony (made up principally by Hydroxyapatite crystals) tooth
Dentin
- connective tissue that contains nerve, blood vessels and lymphatics of the tooth
Pulp
- Region in contact with the gum; Connects crown to root
Neck of the tooth
- portion that protrudes to the bony socket of the jaw
Root of the tooth
โข The shape and size of the tooth varies with the job it has to do
โข There are four different types of tooth:
1. Incisors
2. Canines
3. Pre-molars
4. Molars
These cut and bite food
1. Incisors
These grasp and tear food
2. Canines
These grind and chew food
3. Pre-molars
These also grind and chew food
4. Molars
Processes in the Mouth
โข Mechanical digestion of food- ๐๐๐จ๐ฉ๐๐๐๐ฉ๐๐ค๐ฃ (chewing) of food
โข Mixing masticated food with saliva to form the ๐ฝ๐ค๐ก๐ช๐จ ( ball of food that has been partly digested in the mouth)
โข Initial digestion of carbohydrates
โข Initiation of swallowing by the tongue
โข Allowing for the sense of taste
function Saliva :
Functions of the saliva:
โข Presence of the serous (watery) and mucous secretions which lubricate/ moisten food in the mouth
โข Presence of lysozymes that clean the teeth and inhibit bacterial growth
โข presence of ๐๐ฉ๐ฎ๐๐ก๐๐ฃ๐ or ๐๐ข๐ฎ๐ก๐๐จ๐ that digests a small amount of carbohydrates (starch)
- the largest salivary gland located in the preauricular area
- the parotid duct is known as ๐๐ฉ๐๐ฃ๐จ๐๐ฃ๐จ ๐๐ช๐๐ฉ which exits opposite to the maxillary second molar.
- secrete mainly serous (watery) secretions
1. Parotid gland
- the second largest salivary gland that lies inferior to the body of mandible
- the submandibular duct is known as ๐๐๐๐ง๐ฉ๐ค๐ฃ๐จ ๐๐ช๐๐ฉ which exits at lingual frenulum near the midline.
-secrete both serous (watery) and mucus secretions
2. Submandibular
- the smallest salivary gland that lies deep to the floor of the mouth and exits in multiple ducts.
-secrete both serous (watery) and mucus secretions
3. Sublingual
โข Also known as the throat
โข An area between the oral cavity and esophagus which serves as a common passageway for food, liquids, and air. It is divided into : ๐๐๐จ๐ค๐ฅ๐๐๐ง๐ฎ๐ฃ๐ญ ; ๐๐ง๐ค๐ฅ๐๐๐ง๐ฎ๐ฃ๐ญ; ๐๐๐ง๐ฎ๐ฃ๐๐ค๐ฅ๐๐๐ง๐ฎ๐ฃ๐ญ .
โข Pharyngeal muscles assist in swallowing or ๐ฟ๐๐๐ก๐ช๐ฉ๐๐ฉ๐๐ค๐ฃ
The PHARYNX
โข A muscular tube about 10 inches (25 cm ) long extending from the pharynx to the stomach. It has an ๐ช๐ฅ๐ฅ๐๐ง ๐๐จ๐ค๐ฅ๐๐๐๐๐๐ก ๐จ๐ฅ๐๐๐ฃ๐๐ฉ๐๐ง and ๐ก๐ค๐ฌ๐๐ง ๐๐จ๐ค๐ฅ๐๐๐๐๐๐ก ๐จ๐ฅ๐๐๐ฃ๐๐ฉ๐๐ง . It enters the abdomen through an opening on the right part of the diaphragm.
โข Function: to propel the ๐ฝ๐ค๐ก๐ช๐จ ( ball of food that has been partly digested in the mouth) to the stomach
The ESOPHAGUS
โข Usually J shaped muscular organ located on the left side of the abdominal cavity, anterior to the spleen.
โข It has two curvatures: ๐ฉ๐๐ ๐๐ง๐๐๐ฉ๐๐ง ๐๐ฃ๐ ๐ก๐๐จ๐จ๐๐ง ๐๐ช๐ง๐ซ๐๐ฉ๐ช๐ง๐๐จ.
The STOMACH
โข The stomach is divided into the following regions:
1. Cardiac region
2. Fundus
3. Body of the stomach
4. Pylorus
- where the esophagus enters the stomach
- Food enters at the ๐๐๐ง๐๐๐ค๐๐จ๐ค๐ฅ๐๐๐๐๐๐ก ๐จ๐ฅ๐๐๐ฃ๐๐ฉ๐๐ง (thickened portion at the junction between the stomach and esophagus)
Cardiac region
- the "dome-shape" area and projects upward, and to the left of the cardiac region.
Fundus
- funnel-shaped terminal end of the stomach which has a thick muscular wall called the ๐๐ฎ๐ก๐ค๐ง๐๐ ๐จ๐ฅ๐๐๐ฃ๐๐ฉ๐๐ง that controls the amount of ๐๐๐ฎ๐ข๐ (partly digested semi-fluid food) that goes to the small intestine
Pylorus
The mucous membrane of the stomach is thick and is thrown into numerous gastric folds known as _____.(allow the stomach to expand)
rugae
3 muscle layers of the stomach
1. Oblique (innermost layer)
2. Circular (middle layer)
3. Longitudinal (outermost layer)
Cells found in the stomach
1. Chief cells
2. Parietal cells
3. Goblet cells
4. G-cells
produce ๐๐๐ฅ๐จ๐๐ฃ๐ค๐๐๐ฃ๐จ, the inactivated form of protein-digesting enzymes
Chief cells
produce ๐๐ฎ๐๐ง๐ค๐๐๐ก๐ค๐ง๐๐ ๐๐๐๐ (HCl) which ๐๐๐ฉ๐๐ซ๐๐ฉ๐๐จ ๐ฅ๐๐ฅ๐จ๐๐ฃ๐ค๐๐๐ฃ to become ๐๐๐ฅ๐จ๐๐ฃ that digests protein ; it also secrete ๐๐ฃ๐ฉ๐ง๐๐ฃ๐จ๐๐ ๐๐๐๐ฉ๐ค๐ง needed for ๐๐๐ฉ ๐ฝ 12 ๐๐๐จ๐ค๐ง๐ฅ๐ฉ๐๐ค๐ฃ.
Parietal cells
make mucous which protects the stomach mucosa
Goblet cells
- secrete ๐๐๐จ๐ฉ๐ง๐๐ฃ which plays key role in controlling gastric secretion.
G-cells
๐๐ง๐ค๐ฉ๐๐๐ฃ ๐๐๐๐๐จ๐ฉ๐๐ค๐ฃ starts at the stomach by the action of ______
Pepsin
โข The bodys major digestive organ
โข Site of nutrient absorption into the blood
โข Muscular tube extending form the pyloric sphincter to the ileocecal valve
The SMALL INTESTINES
3 part Subdivisions of the Small Intestine
1. Duodenum
2. Jejunum
3. Ileum
โข C- shape tube that joins the stomach to the jejunum. The shortest part of the small intestine (about 10 inches long)
โข Curves around the head of the pancreas
โข It receives the bile and the pancreatic ducts.
Duodenum
Attaches anteriorly to the duodenum
Jejunum
โข Extends from jejunum to the cecum (large intestine)
โข At the ๐๐ก๐๐ค๐๐๐๐๐ก ๐๐ช๐ฃ๐๐ฉ๐๐ค๐ฃ, the opening is guarded by folds or lips known as the Ileocecal valve which regulates the amount of materials that can pass from the small intestine to the large intestine
Ileum
The surface area inside the small intestine is greatly increased by _______
1. circular folds
2. villi
3. microvilli.
The small intestines has a permanent circular folds known as ________.
plicae circulares
The ______ of the Small Intestine
โข Fingerlike structures formed by the mucosa
โข Give the small intestine more surface area
Villi
The ______ of the Small Intestine
โข Small projections of the plasma membrane (brush border)
โข Found on absorptive cells
(villi > absorptive cells> microvilli)
Microvilli
_____ is produced by the ๐ก๐๐ซ๐๐ง and stored temporarily in the ๐๐๐ก๐ก ๐๐ก๐๐๐๐๐ง which are released for ๐๐๐ฉ ๐๐๐๐๐จ๐ฉ๐๐ค๐ฃ
Bile
The partly digested fats are coated by bile to form "droplets" called _____ which can now easily absorb by the intestinal mucosa.
micelles
______ is also produced by the pancreas to neutralize the acidic chyme as it enters the small intestines
Bicarbonate
Extends from the ileum to the anus. Larger in diameter, but shorter than the small intestine
The LARGE INTESTINES
Frames the internal abdomen
It is divided into:
1. Cecum
โข saclike first part of the large intestine
โข Appendix
- Hangs from the cecum
- Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)
2. Ascending colon
3. Transverse colon
4. Descending colon
5. Sigmoid colon
6. Rectum
7. Anus
Functions of the Large Intestine
โข Absorption of water
โข Eliminates indigestible food from the body as feces
โข Does not participate in digestion of food
โข No digestive enzymes are produced
โข Goblet cells produce mucus to act as a lubricant
โข Resident bacteria digest remaining nutrients
โขProduce some vitamin K and B
โข Release gases
โข Water and vitamins K and B are absorbed
โข Remaining materials are eliminated via feces
โข The feces consists of:
75% water ;
25% solid matter, of which 30% is bacteria, and 30% undigested fiber
The longitudinal muscles in the large intestines becomes three flat bands known as _______ which converge on the base of the appendix
Teniae coli
- or sac-like projections are found in the walls of the large intestine
Haustrations
The large intestine has fatty tags called the __________.
appendices epiploicae
presence of _____________that digests a small amount of carbohydrates (starch)
๐๐ฉ๐ฎ๐๐ก๐๐ฃ๐ or ๐๐ข๐ฎ๐ก๐๐จ๐
โข Pharyngeal muscles assist in swallowing or _________
๐ฟ๐๐๐ก๐ช๐ฉ๐๐ฉ๐๐ค๐ฃ
3 major salivary gland
1. parotid gland
2. submandibular
3. sublingual
the parotid duct is known as____________ which exits opposite to the maxillary second molar.
Stensenโs duct
the submandibular duct is known as ___________ which exits at lingual frenulum near the midline.
Whartonโs duct