Notes for anatomy

1. DIGESTIVE SYSTEM

2. OBJECTIVES:
 Will be able to identify the parts of the Digestive system
 Discuss the functions of each part of the system
 Discuss the physiology of digestive system

3. What is Digestive system?
(Gastrointestinal tract)
 An organ system within humans and other animals which takes in food, digests it and absorb
energy and nutrients, and expels the remaining waste as feces.
 The Major organs of the digestive system
 Mouth
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Rectum
• Accessory digestive system
 Liver
 Gallbladder
 Pancreas
 Salivary gland

4. FUNCTIONS OF DIGESTIVE SYSTEM
• Ingestion - taking of food into the alimentary tract.
i.e. eating & drinking
• Propulsion – mixes & moves the contents along the alimentary tract.
• Digestion – consist of:
 Mechanical breakdown of food e.g. mastication(chewing)
 Chemical digestion of food into small molecules by enzymes
• Absorption – this is the process by which digested food substances pass through the
walls of some organs of the alimentary canal into the blood for circulation.
• Elimination – food substances that have been eaten but cannot be digested & absorbed
are excreted from the alimentary canal as feces by the process defaecation.

5. MOUTH
-Digestion begins even before the food enters the mouth. When a
person smells or think of food or eating, the salivary glands begin
producing saliva.
 Receives the food and produces saliva
Once the food is inside the mouth:
 Saliva moistens it
 The teeth and tongue break it down mechanically.
 An enzyme in the saliva, salivary amylase, breaks it down into starch.

6. Tongue
• A muscular organ in the mouth, that
manipulates food for mastication,
and used in the act of swallowing.
• The primary organ of taste in the
gustatory system
Functions:
• Mastication (chewing)
• Deglutition(swallowing)
• Speech
• taste

7. TEETH
• Function to mechanically break down
items of food by cutting and crushing
them in preparation for swallowing and
digesting.
 Primary set of teeth:
1. 10 on the maxilla(upper jaw)
2. 10 on the mandible(lower jaw)
 Permanent teeth
1. 16 on the maxilla
2. 16 on the mandible
Composed of:
• Two incisor(for cutting)
• One canine(for tearing)
• Two premolar(for crushing)
• Three molar(for grinding)

8. SALIVARY GLANDS
• Produces saliva
3 paired major saliva glands:
 Parotid –
• Wrapped around the mandibular ramus in humans
• The largest salivary glands
• Secretes saliva to facilitate mastication and swallowing
 Submandibular
• Located beneath the lower jaws, superior to the digastric
muscles
• The secretion produce mixture of both serous fkuid and
mucus
 Sublingual
• Located inferior to the tongue, anterior to the
submandibular gland
• Where Approximately 5% of saliva entering the oral cavity
comes from
• Secretion produced is mainly mucous in nature

9. COMPOSITION OF SALIVA:
• About 1.5 litres of saliva is produced daily & it consists of:
 Water
 Mineral salts
 An enzymes
 Mucus
 Lysozyme
 Immunoglobulins
FUNCTIONS OF SALIVA:
• Lubricant
 Coats oral mucosa, mechanically protecting it from trauma during eating, swallowing and speaking
• Digestion
 Moistening food and helping to create a food bolus
 Allows the food bolus to be passed easily from the mouth into the esophagus
• Role taste
 The liquid medium in which chemicals are carried to taste receptor cells(mostly associated with inguinal
papillae)

10. THE PHARYNX
• The pharynx is the part of the throat that is behind the mouth and nasal cavity and above the
esophagus and the larynx, or the tubes going down to the stomach and the lungs.
• The portion of the digestive tract that receives the food from your mouth.
• Branching off the pharynx is the esophagus, which carries food to the stomach.

11. THE ESOPHAGUS
• The esophagus or oesophagus, commonly known as the food pipe or gullet, is a muscular tube
connecting the throat(pharynx) with the stomach
• Runs behind the windpipe(trachea) and heart, and in front of the spine.
• Length : 25 cm
• Diameter : 2 cm
• Partly skeletal and partly smooth muscles
 the upper part is entirely skeletal
(2-4 cm)
 The middle, a mixture of skeletal and
Smooth muscle
 The lower part, 11 cm or in length is
Entirely smooth

12. STRUCTURE
The esophagus is about 8 inches long, and is lined by
moist pink tissue called mucosa. The esophagus runs
behind the windpipe (trachea) and heart, and in front
of the spine. Just before entering the stomach, the
esophagus passes through the diaphragm.
The upper esophageal sphincter (UES) is a bundle of
muscles at the top of the esophagus. The muscles of
the UES are under conscious control, used when
breathing, eating, belching, and vomiting. They keep
food and secretions from going down the windpipe.
The lower esophageal sphincter (LES) is a bundle of
muscles at the low end of the esophagus, where it
meets the stomach. When the LES is closed, it
prevents acid and stomach contents from traveling
backwards from the stomach. The LES muscles are
not under voluntary control.

13. STOMACH
• A pouch-like organ, primarily designed for food storage(for 2-4 hours)
• Where some mechanical and chemical digestion occur.
• A muscular organ located on the left side of the upper abdomen. The stomach receives food from
the esophagus

14. • Contains two sphincters at both ends to regulate food movement:
 Cardiac sphincter near the esophagus,
 Pyloric sphincter near the small intestine
• It is divided into four regions:
 Cardiac stomach (or cardia)
 Fundic stomach (or funded)
 Body of stomach
 Pyloric stomach (or pylorus)
FUNCTIONS
• Digestion
 Releases proteases(protein-digesting enzymes
such as pepsin) and hydrochloric acid, which
kills or inhibits bacteria and provides the
acidic pH of 2 for the proteases to work.
 Food is churned through muscular
contractions of the wall called peristalsis

15. GASTRIC JUICE
• Gastric acid or stomach acid, is a digestive fluid formed in the stomach
 Hydrochloric acid(HCl)
 Potassium chloride(KCl)
 Sodium chloride(NaCl)
• Digesting of proteins, by activating digestive enzymes, and making ingested proteins unravel so that
digestive enzymes break down the long chains of amino acids

16. THE PANCREAS
• A glandular organ in the digestive system and endocrine system of vertebrates
• Located in the abdominal cavity behind the stomach
• An endocrine gland that Produce several important hormones, including:
 Insulin
 Glucagon
 Samatostatin
 Pancreatic polypeptide and all of which circulate on the blood
• Length: 15 cm or 6 inch

17. STRUCTURE
• Divided into:
 the head
 The neck
 The body
 The tail
• The neck is about 2.5 cm or 1 inch long lies between the head and the body
• The body is the largest part, that lies between the pylorous
• The tail ends by abutting the spleen
FUNCTION
• blood sugar control and metabolism
• your pancreas makes pancreatic juices called enzymes. These enzymes break down sugars, fats, and
starches.

18. THE LIVER
• the largest solid organ in the body.
• removes toxins from the body's blood supply, maintains healthy blood sugar levels, regulates blood
clotting, and performs hundreds of other vital functions.
• filter the blood coming from the digestive tract, before passing it to the rest of the body. The liver also
detoxifies chemicals and metabolizes drugs. As it does so, the liver secretes bile that ends up back in
the intestines.

19. PARTS
The following are some of the most important individual parts of the liver:
Common Hepatic Duct: A tube that carries bile out of the liver.
It is formed from the intersection of the right and left hepatic ducts.
Falciform Ligament: A thin, fibrous ligament that separates
the two lobes of the liver and connects it to the abdominal wall.
Glisson’s Capsule: A layer of loose connective tissue that
surrounds the liver and its related arteries and ducts.
Hepatic Artery: The main blood vessel that supplies the
liver with oxygenated blood.
Hepatic Portal Vein: The blood vessel that carries blood
from the gastrointestinal tract, gallbladder, pancreas,
and spleen to the liver.
Lobes: The anatomical sections of the liver.
Lobules: Microscopic building blocks of the liver.
Peritoneum: A membrane covering the liver that forms
the exterior.

20. THE GALLBLADDER
• A small hollow organ where bile is stored and concentrated before it is released into the small
intestine
• In the humans, the pear-shaped gallbladder lies beneath the liver
• Stores bile, also called gall, needed for the digestion of fats in food
STRUCTURE
• Is grey-blue in life
• Length: 7-10 cm or 2.8 to 3.9 inches
• Diameter: 4 cm or 1.6 inch
• Has the capacity of about 50 millilitres
• Is shaped like pear, with its tip opening into
• the cystic duct
• Divided into three sections:
 The fundus is the rounded base,
angled so that it faces the abdominal wall
 The body lies in a depression in the
 surface of the lower liver.
 The neck tapers and is continuous with
 the cystic dust, part of the biliary tree

21. THE SMALL INTESTINE
• Also called as small bowel, is the part of the gastrointestinal tract between the stomach and the large
intestine, where most of the end absorption of food takes place
• Digestion of protein & carbohydrates
• Digested food is now able to pass into the blood vessels in the wall of the intestine though either diffusion
or active transport
• Supports the body’s immune system

22. PARTS
• It is divided into three structural parts
 (I) The duodenum
 is a short structure ranging from 20 cm to 25 cm in length, and shaped like a “C”
 the first part of the small intestine.
 It connects to the stomach. The duodenum helps to further digest food coming from the stomach. It
absorbs nutrients (vitamins, minerals, carbohydrates, fats, proteins) and water from food so they can be
used by the body.
 (II) The jejunum
 The midsection of the small intestine, connecting
 the duodenum to the ileum. It is about
2.5 m long.
 absorb sugars, amino acids, and fatty acids.
 (III) The ileum
 The final section of the small intestine
 It is about 3 m long, and contains villi
similar to the jejunum
 It connects to the cecum (first part of the
large intestine).

23. THE LARGE INTESTINE
• Also know as the large bowel or colon, is the large part of the gastrointestinal tract and of the digestive
system in vertebrates
• Water is absorbed here and the remaining waste material is stored as feces before being removed as
defecation

24. STRUCTURE
• Length:
Male: 166 cm
Female: 155 cm
• Consist of five sections:
 The Cecum
 The first section of the colon and involved
in the digestion, while the appendix is
a structure of the colon, not involved in digestion

25.  The ascending colon
 Is connected to the small intestine by a
section of bowel called cecum
 Moves the unwanted waste material upward
the transverse colon by the action peristalsis
 Peristalsis is a radially symmetrical contraction
and relaxation of muscles that propagates in a
wave down a tube
 Approximately over eight inches or 20 cm
 Transverse colon
 The part of the colon from the
hepatic failure to the splenic flexure
 As the longest and most mobile part
of the colon, the transverse colon plays an
essential role in digestion and the excretion
of waste products.

26.  Descending colon
 Also called as distal gut
 Store feces that will be emptied
into the rectum
 Sigmoid colon
 Is after the descending colon and before the
rectum
 Sigmoid means S-shaped
 the walls are muscular, and contract to increase
the pressure inside the colon, causing the stool to
move into the rectum.

27.  Rectum
 the last section of the large intestine
 Holds the formed feces awaiting elimination via
defecation
 The anus
 The external opening of the rectum
 Controls expulsion of feces
 Two sphincters that controls the exit of feces from the
body during an act of defecation
o Internal anal sphincter and external anal sphincter
,which are circular muscle that normally maintain
constriction of the orifice and which relaxes as required
by normal physiological functioning

28. PHYSIOLOGY OF DIGESTION
• The mouth is the beginning of the digestive tract
• Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin
the process of breaking it down
• From pharynx, food travels to the esophagus or swallowing tube
• By means of a series of contraction, called peristalsis, the esophagus delivers the food to the stomach
• the lower esophageal sphincter keep food from passing backwards into the esophagus
• The stomach secretes acid and powerful enzymes that continue the process of breaking down the food
• After the food gets through the stomach, the food has the consistency of a liquid or paste
• Then it moves to the small intestine
• After the food is broken down by using enzymes released by pancreas and bile from the liver
• Bile is a compound that aids in the digestion of fat and eliminates waste products from the blood
• Then is passes through the large intestines
• Then stool, or waste left over from the digestive process, is passed through the colon by means or
peristalsis, first in liquid state and ultimately in solid from as the water is removed from the stool
• As stool is stored in the sigmoid colon until a “mass movement” empties it into the rectum once or
twice a day.

29. “
”
THANK YOU!!!