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
• An ______ is a biological catalyst that speeds up chemical reactions
• 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. 𝙀𝙖𝙩𝙞𝙣𝙜 (also called 𝙞𝙣𝙜𝙚𝙨𝙩𝙞𝙤𝙣)
2. 𝘿𝙞𝙜𝙚𝙨𝙩𝙞𝙤𝙣 (Breakdown of ingested food)
3. 𝘼𝙗𝙨𝙤𝙧𝙥𝙩𝙞𝙤𝙣 (Passage of nutrients into the blood)and Metabolism (Production of cellular energy (𝘼𝙏𝙋")
4. 𝙀𝙡𝙞𝙢𝙞𝙣𝙖𝙩𝙞𝙤𝙣 of undigested food (also called "𝙚𝙜𝙚𝙨𝙩𝙞𝙤𝙣")
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 (𝘼𝙡𝙞𝙢𝙚𝙣𝙩𝙖𝙧𝙮 𝙘𝙖𝙣𝙖𝙡)
Structures of digestive:
• Mouth/ Oral Cavity
• Pharynx
• Esophagus
• Stomach
• intestines
Accessory structures of digestive:
• Salivary glands
• Liver
• Gall bladder
• Pancreas
The contents of the 𝙖𝙡𝙞𝙢𝙚𝙣𝙩𝙖𝙧𝙮 𝙘𝙖𝙣𝙖𝙡 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
•Lips (labia)
• form the lateral walls
Cheeks
• forms the anterior roof
Hard palate
• forms the posterior roof
Soft palate
• fleshy projection of the soft palate
Uvula
• space between lips externally and teeth and gums internally
Vestibule
• area contained by the teeth
Oral cavity
• attached at hyoid and styloid processes of the skull, and by the lingual 𝙛𝙧𝙚𝙣𝙪𝙡𝙪𝙢. It contains the receptor for taste.
Tongue
• lymphoid tissue, part of body defense system
- Palatine tonsils
- Lingual tonsil
Tonsils
• An adult human has _____ 𝙩𝙚𝙚𝙩𝙝,
32
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
• The shape and size of the tooth varies with the job it has to do
• 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
• Mechanical digestion of food- 𝙈𝙖𝙨𝙩𝙞𝙘𝙖𝙩𝙞𝙤𝙣 (chewing) of food
• Mixing masticated food with saliva to form the 𝘽𝙤𝙡𝙪𝙨 ( ball of food that has been partly digested in the mouth)
• Initial digestion of carbohydrates
• Initiation of swallowing by the tongue
• Allowing for the sense of taste
function Saliva :
Functions of the saliva:
• Presence of the serous (watery) and mucous secretions which lubricate/ moisten food in the mouth
• Presence of lysozymes that clean the teeth and inhibit bacterial growth
• presence of 𝙋𝙩𝙮𝙖𝙡𝙞𝙣𝙚 or 𝙖𝙢𝙮𝙡𝙖𝙨𝙚 that digests a small amount of carbohydrates (starch)
- the largest salivary gland located in the preauricular area
- the parotid duct is known as 𝙎𝙩𝙚𝙣𝙨𝙚𝙣𝙨 𝙙𝙪𝙘𝙩 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 𝙒𝙝𝙖𝙧𝙩𝙤𝙣𝙨 𝙙𝙪𝙘𝙩 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
• Also known as the throat
• An area between the oral cavity and esophagus which serves as a common passageway for food, liquids, and air. It is divided into : 𝙉𝙖𝙨𝙤𝙥𝙝𝙖𝙧𝙮𝙣𝙭 ; 𝙊𝙧𝙤𝙥𝙝𝙖𝙧𝙮𝙣𝙭; 𝙇𝙖𝙧𝙮𝙣𝙜𝙤𝙥𝙝𝙖𝙧𝙮𝙣𝙭 .
• Pharyngeal muscles assist in swallowing or 𝘿𝙚𝙜𝙡𝙪𝙩𝙞𝙩𝙞𝙤𝙣
The PHARYNX
• A muscular tube about 10 inches (25 cm ) long extending from the pharynx to the stomach. It has an 𝙪𝙥𝙥𝙚𝙧 𝙚𝙨𝙤𝙥𝙝𝙖𝙜𝙚𝙖𝙡 𝙨𝙥𝙝𝙞𝙣𝙘𝙩𝙚𝙧 and 𝙡𝙤𝙬𝙚𝙧 𝙚𝙨𝙤𝙥𝙝𝙖𝙜𝙚𝙖𝙡 𝙨𝙥𝙝𝙞𝙣𝙘𝙩𝙚𝙧 . It enters the abdomen through an opening on the right part of the diaphragm.
• Function: to propel the 𝘽𝙤𝙡𝙪𝙨 ( ball of food that has been partly digested in the mouth) to the stomach
The ESOPHAGUS
• Usually J shaped muscular organ located on the left side of the abdominal cavity, anterior to the spleen.
• It has two curvatures: 𝙩𝙝𝙚 𝙜𝙧𝙚𝙖𝙩𝙚𝙧 𝙖𝙣𝙙 𝙡𝙚𝙨𝙨𝙚𝙧 𝙘𝙪𝙧𝙫𝙖𝙩𝙪𝙧𝙚𝙨.
The STOMACH
• 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 𝙘𝙖𝙧𝙙𝙞𝙤𝙚𝙨𝙤𝙥𝙝𝙖𝙜𝙚𝙖𝙡 𝙨𝙥𝙝𝙞𝙣𝙘𝙩𝙚𝙧 (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 𝙋𝙮𝙡𝙤𝙧𝙞𝙘 𝙨𝙥𝙝𝙞𝙣𝙘𝙩𝙚𝙧 that controls the amount of 𝙘𝙝𝙮𝙢𝙚 (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 𝙋𝙚𝙥𝙨𝙞𝙣𝙤𝙜𝙚𝙣𝙨, the inactivated form of protein-digesting enzymes
Chief cells
produce 𝙝𝙮𝙙𝙧𝙤𝙘𝙝𝙡𝙤𝙧𝙞𝙘 𝙖𝙘𝙞𝙙 (HCl) which 𝙖𝙘𝙩𝙞𝙫𝙖𝙩𝙚𝙨 𝙥𝙚𝙥𝙨𝙞𝙣𝙤𝙜𝙚𝙣 to become 𝙋𝙚𝙥𝙨𝙞𝙣 that digests protein ; it also secrete 𝙞𝙣𝙩𝙧𝙞𝙣𝙨𝙞𝙘 𝙛𝙖𝙘𝙩𝙤𝙧 needed for 𝙑𝙞𝙩 𝘽 12 𝙖𝙗𝙨𝙤𝙧𝙥𝙩𝙞𝙤𝙣.
Parietal cells
make mucous which protects the stomach mucosa
Goblet cells
- secrete 𝙂𝙖𝙨𝙩𝙧𝙞𝙣 which plays key role in controlling gastric secretion.
G-cells
𝙋𝙧𝙤𝙩𝙚𝙞𝙣 𝙙𝙞𝙜𝙚𝙨𝙩𝙞𝙤𝙣 starts at the stomach by the action of ______
Pepsin
• The bodys major digestive organ
• Site of nutrient absorption into the blood
• 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
• C- shape tube that joins the stomach to the jejunum. The shortest part of the small intestine (about 10 inches long)
• Curves around the head of the pancreas
• It receives the bile and the pancreatic ducts.
Duodenum
Attaches anteriorly to the duodenum
Jejunum
• Extends from jejunum to the cecum (large intestine)
• At the 𝙞𝙡𝙚𝙤𝙘𝙚𝙘𝙖𝙡 𝙟𝙪𝙣𝙘𝙩𝙞𝙤𝙣, 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
• Fingerlike structures formed by the mucosa
• Give the small intestine more surface area
Villi
The ______ of the Small Intestine
• Small projections of the plasma membrane (brush border)
• Found on absorptive cells
(villi > absorptive cells> microvilli)
Microvilli
_____ is produced by the 𝙡𝙞𝙫𝙚𝙧 and stored temporarily in the 𝙜𝙖𝙡𝙡 𝙗𝙡𝙖𝙙𝙙𝙚𝙧 which are released for 𝙛𝙖𝙩 𝙙𝙞𝙜𝙚𝙨𝙩𝙞𝙤𝙣
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
• saclike first part of the large intestine
• 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
• Absorption of water
• Eliminates indigestible food from the body as feces
• Does not participate in digestion of food
• No digestive enzymes are produced
• Goblet cells produce mucus to act as a lubricant
• Resident bacteria digest remaining nutrients
•Produce some vitamin K and B
• Release gases
• Water and vitamins K and B are absorbed
• Remaining materials are eliminated via feces
• 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)
𝙋𝙩𝙮𝙖𝙡𝙞𝙣𝙚 or 𝙖𝙢𝙮𝙡𝙖𝙨𝙚
• Pharyngeal muscles assist in swallowing or _________
𝘿𝙚𝙜𝙡𝙪𝙩𝙞𝙩𝙞𝙤𝙣
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.
Stensen’s duct
the submandibular duct is known as ___________ which exits at lingual frenulum near the midline.
Wharton’s duct