Anatomy%20-%20Digestive%20System%20part%20I.pdf.pdf

Digestive system anatomy

1. Digestive System
part I
Anatomy

2. General Concept
The digestive system consists of
•digestive tract, a tube extending from the
mouth to the anus,
•and accessory organs—primarily glands
located outside the digestive tract that secrete
fluids into it.

3. General Concept
The regions of the digestive tract include the following:
•Oral cavity, or mouth, with the salivary glands and tonsils
as accessory organs
•Pharynx, or throat
•Esophagus
•Stomach
•Small intestine, consisting of the duodenum, jejunum, and
ileum, with the liver, gallbladder, and pancreas as major
accessory organs
•Large intestine, including the cecum, colon, rectum, and
anal canal
•Anus

5. Functions of the Digestive System
•Ingestion is the intake of solid or liquid food
into the stomach. The normal route of
ingestion is through the oral cavity.
•Mastication is the process by which the teeth
chew food in the mouth. It is vital, therefore,
that solid foods be mechanically broken down
by mastication into smaller particles to
increase the total surface area of food for
digestion.

6. Functions of the Digestive System
•Propulsion of food from one end of the digestive tract to
the other. The total time it takes food to travel the length of
the digestive tract is usually about 24–36 hours. Each
segment of the digestive tract is specialized to assist in
moving its contents from the oral end to the anal end:
•Swallowing, or deglutition moves liquids or a soft mass of
food and liquid, called a bolus, from the oral cavity into the
esophagus.
•Mass movements are contractions that move material in
some parts of the large intestine. Mass movements extend
over much larger parts of the digestive tract than peristaltic
movements.

7. Functions of the Digestive System
•Peristalsis propels material through most of the
digestive tract. Peristaltic waves are muscular
contractions consisting of a wave of relaxation of
the circular muscles in front of the bolus, followed
by a wave of strong contraction of the circular
muscles behind the bolus, which force the bolus
along the digestive tube. Each peristaltic wave
travels the length of the esophagus in about 10
seconds. Peristaltic waves in the small intestine
usually travel only short distances.

8. Peristalsis

9. Functions of the Digestive System
•Mixing. Some contractions do not propel food from one end of the
digestive tract to the other but, rather, move it back and forth within the
digestive tract to mix it with digestive secretions and help break it into
smaller pieces. Segmental contractions are mixing contractions that occur
in the small intestine.
•Secretion. As food moves through the digestive tract, secretions are added
to lubricate, liquefy, buffer, and digest the food. Mucus, secreted along
the entire digestive tract, lubricates the food and the lining of the tract.
The mucus coats and protects the epithelial cells of the digestive tract
from mechanical abrasion, stomach acid, and digestive enzymes. The
secretions also contain large amounts of water, which liquefies the food,
making it easier to digest and absorb. Liver secretions break large lipid
droplets into much smaller droplets, which makes the digestion and
absorption of lipids possible. Enzymes secreted by the oral cavity,
stomach, small intestine, and pancreas break down large food molecules
into smaller molecules that can be absorbed by the intestinal wall.

10. Segmental Contraction

11. Functions of the Digestive System
•Digestion is the breakdown of large organic molecules into their
component parts: carbohydrates into monosaccharides, proteins into
amino acids, and triglycerides into fatty acids and glycerol. Digestion
consists of mechanical digestion, which involves the mastication and
mixing of food, and chemical digestion, which is accomplished by
digestive enzymes secreted along the digestive tract.
•Absorption is the movement of molecules out of the digestive tract and
into the circulation or into the lymphatic system. The mechanism by which
absorption occurs depends on the type of molecule involved. Molecules
pass out of the digestive tract by diffusion, facilitated diffusion, active
transport, symport, or endocytosis.
•Elimination is the process by which the waste products of digestion are
removed from the body. During this process, which occurs primarily in the
large intestine, water and salts are absorbed, changing the material in the
digestive tract from liquefied to semi-solid. These semi-solid waste
products, called feces, are then eliminated from the digestive tract by the
process of defecation.

30. Oral Cavity

31. Oral Cavity
The oral cavity, or mouth, is divided into two regions:
•The vestibule is the space between the teeth and gingivae (gums) and
the lips and cheeks. The vestibule communicates with the exterior through the
oral fissure (opening), the size of which is controlled by the perioral muscles,
such as the orbicularis oris (the sphincter of the oral fissure), the buccinator,
risorius, and depressors and elevators of the lips (dilators of the fissure).
•The oral cavity proper is the space between the upper and
the lower dental arches or arcades (maxillary and mandibular
alveolar arches and the teeth they bear). The roof of the oral cavity
is formed by the palate. Posteriorly, the oral cavity communicates
with the oropharynx (oral part of the pharynx). When the mouth is
closed and at rest, the oral cavity is fully occupied by the tongue.

33. Oral vestibule and gingivae. A. The vestibule and gingivae of the maxilla are shown.
B. The vestibule and gingivae of the mandible are shown. As the alveolar mucosa
approaches the necks of the teeth, it changes in texture and color to become the
gingiva proper.

34. Oral Cavity

35. Lips and Cheeks
•LIPS
The lips, or labia, are fibromuscular structures formed
mostly by the orbicularis oris muscle and connective
tissue. The outer surfaces of the lips are covered by skin.
The color from the underlying blood vessels shows
through the relatively transparent epithelium, giving the
lips a reddish-pink to dark red appearance, depending on
the overlying pigment.
One or more labial frenula, which are mucosal folds,
extend from the alveolar process of the maxilla to the
upper lip and from the alveolar process of the mandible
to the lower lip.

36. LIPS

37. Blood, Nerve and Lymphatic Supply
•The superior and inferior labial arteries, branches of the facial
arteries, anastomose with each other in the lips to form an arterial
ring. The pulse of these arteries may be palpated by grasping the
upper or lower lip lightly between the first two digits.
•The upper lip is supplied by superior labial branches of the facial
and infra-orbital arteries. The lower lip is supplied by inferior labial
branches of the facial and mental arteries.
•The upper lip is supplied by the superior labial branches of the
infra-orbital nerves (of CN V2 – Maxillary nerve), and the lower lip
is supplied by the inferior labial branches of the mental nerves (of
CN V3 – Mandibular Nerve).
•Lymph from the upper lip and lateral parts of the lower lip passes
primarily to the submandibular lymph nodes, whereas lymph from
the medial part of the lower lip passes initially to the submental
lymph nodes.

39. Blood Supply

40. Lymphatics

41. Innervation

42. Innervation

43. Lips, Cheeks, and Gingivae
•Cheeks
The cheeks form the lateral walls of the oral cavity.
The interior of the cheek includes the buccinator
muscle, which flattens the cheek against the teeth,
and the buccal fat pad, which rounds out the profile
on the side of the face. The lips and cheeks are
important in mastication and speech. They help
manipulate food within the oral cavity and hold it in
place while the teeth crush or tear it. They also help
form words when we speak.

44. Cheeks

45. Lips and Cheeks

46. Blood supply and innervation
•The cheeks are supplied by buccal branches of
the maxillary artery.
•Innervated by buccal branches of the
mandibular nerve.

47. Blood supply and innervation

48. Palate
The roof of the oral cavity is called the palate. The palate
separates the oral and nasal cavities and prevents food from
passing into the nasal cavity during chewing and swallowing.
The palate consists of two parts:
•The anterior, bony part is the hard palate.
•The posterior, nonbony part is the soft palate, which
consists of skeletal muscle and connective tissue.
The uvula is a posterior projection from the soft palate. The
posterior boundary of the oral cavity is the fauces, or throat,
which is the opening into the pharynx. The palatine tonsils are
in the lateral wall of the fauces.
•The fauces (L. throat) is the space between the oral cavity
and the pharynx.

49. Muscles of Soft Palate

50. Tongue
•The tongue is a mobile muscular organ
covered with mucous membrane. It can
assume a variety of shapes and positions. It is
partly in the oral cavity and partly in the
oropharynx. The tongue’s main functions are
articulation (forming words during speaking)
and squeezing food into the oropharynx as
part of deglutition (swallowing). The tongue is
also involved with mastication, taste, and oral
cleansing.

51. PARTS OF TONGUE
The tongue has a root, body, and apex.
•The root of the tongue is the attached posterior
portion, extending between the mandible, hyoid, and
the nearly vertical posterior surface of the tongue.
•The body of the tongue is the anterior, approximately
two thirds of the tongue between root and apex.
•The apex (tip) of the tongue is the anterior end of the
body, which rests against the incisor teeth. The body
and apex of the tongue are extremely mobile.

52. PARTS OF TONGUE

53. MUSCLES OF TONGUE
The tongue is a mass of muscles that is mostly
covered by mucosa.
In general, extrinsic muscles alter the position of
the tongue, and intrinsic muscles alter its shape.
The four intrinsic and four extrinsic muscles in
each half of the tongue are separated by a
median fibrous lingual septum, which merges
posteriorly with the lingual aponeurosis.

55. MUSCLES OF TONGUE
Extrinsic Muscles of Tongue. The extrinsic
muscles of the tongue (genioglossus,
hyoglossus, styloglossus, and palatoglossus)
originate outside the tongue and attach to it.
They mainly move the tongue but they can alter
its shape as well.

57. MUSCLES OF TONGUE
Intrinsic Muscles of Tongue. The superior and
inferior longitudinal, transverse, and vertical
muscles are confined to the tongue. They have their
attachments entirely within the tongue and are not
attached to bone. The superior and inferior
longitudinal muscles act together to make the
tongue short and thick and to retract the protruded
tongue. The transverse and vertical muscles act
simultaneously to make the tongue long and
narrow, which may push the tongue against the
incisor teeth or protrude the tongue from the open
mouth.

59. MUSCLES OF TONGUE

60. Extrinsic Muscles of Tongue

61. Intrinsic Muscles of Tongue

62. INNERVATION OF TONGUE
All muscles of the tongue, except the palatoglossus, receive motor
innervation from CN XII, the hypoglossal nerve.
For general sensation (touch and temperature), the mucosa of the anterior
two thirds of the tongue is supplied by the lingual nerve, a branch of CN V3.
For special sensation (taste), this part of the tongue, except for the vallate
papillae, is supplied the chorda tympani nerve, a branch of CN VII.
The mucosa of the posterior third of the tongue and the vallate papillae are
supplied by the lingual branch of the glossopharyngeal nerve (CN IX) for both
general and special sensation.
Sensory nerves carry parasympathetic secretomotor fibers to serous glands
in the tongue. There are four basic taste sensations: sweet, salty, sour, and
bitter. Sweetness is detected at the apex, saltiness at the lateral margins, and
sourness and bitterness at the posterior part of the tongue. All other “tastes”
expressed by gourmets are olfactory (smell and aroma).

64. INNERVATION OF TONGUE

65. VASCULATURE OF TONGUE
The arteries of the tongue are derived from the lingual artery, which arises
from the external carotid artery. On entering the tongue, the lingual artery
passes deep to the hyoglossus muscle.
The dorsal lingual arteries supply the root of the tongue; the deep lingual
arteries supply the lingual body. The deep lingual arteries communicate with
each other near the apex of the tongue.
The veins of the tongue are the dorsal lingual veins, which accompany the
lingual artery; the deep lingual veins, which begin at the apex of the tongue,
run posteriorly beside the lingual frenulum to join the sublingual vein.
The sublingual veins in elderly people are often varicose (enlarged and
tortuous).
Some or all of them may drain into the IJV, or they may do so indirectly,
joining first to form a lingual vein that accompanies the initial part of the
lingual artery.

67. VASCULATURE OF TONGUE
The lymphatic drainage of the tongue is exceptional. Most of the
lymphatic drainage converges toward and follows the venous drainage;
however, lymph from the tip of the tongue, frenulum, and central lower
lip runs an independent course. Lymph from the tongue takes four routes:
•1. Lymph from the root drains bilaterally into the superior deep
cervical lymph nodes.
•2. Lymph from the medial part of the body drains bilaterally and
directly to the inferior deep cervical lymph nodes.
•3. Lymph from the right and left lateral parts of body drains to the
submandibular lymph nodes on the ipsilateral side.
•4. The apex and frenulum drain to the submental lymph nodes, the
medial portion draining bilaterally.
All lymph from the tongue ultimately drains to the deep cervical nodes,
and passes via the jugular venous trunks into the venous system at the
right and left venous angles.

69. VASCULATURE OF TONGUE

70. Teeth
Adults normally have 32 teeth, which are distributed in two dental arches: the
maxillary arch and the mandibular arch.
The teeth in the right and left halves of each dental arch are roughly mirror images of
each other.
The teeth are apportioned into four quadrants: right-upper, left-upper, right-lower,
and left-lower.

71. Teeth
The teeth in each quadrant include:
•one central and one lateral incisor,
•one canine,
•first and second premolars,
•first, second, and third molars.
The third molars are often called wisdom teeth because they
usually appear in the late teens or early twenties, when a
person is old enough to have acquired some wisdom. In
people with small dental arches, the third molars may not
have room to erupt into the oral cavity and remain embedded
within the jaw.

72. Teeth

73. Teeth
Embedded wisdom teeth are referred to as impacted
and may cause pain or irritation. Usually, the impacted
wisdom teeth are surgically removed.
The teeth of the adult mouth are called permanent
teeth, or secondary teeth. Most of them are
replacements for deciduous teeth, or primary teeth, also
called milk teeth, which are lost during childhood.
The deciduous teeth erupt (the crowns appear within the
oral cavity) between about 6 months and 24 months of
age. The permanent teeth begin replacing the deciduous
teeth at about 5 years, and the process is completed by
about 11 years.

74. Teeth

75. VASCULATURE OF TEETH
The superior and inferior alveolar arteries,
branches of the maxillary artery, supply the
maxillary and mandibular teeth, respectively.
The alveolar veins have the same names and
distribution accompany the arteries.
Lymphatic vessels from the teeth and gingivae pass
mainly to the submandibular lymph nodes.

77. VASCULATURE OF TEETH

78. VASCULATURE OF TEETH

79. Lymphatic vessels

80. INNERVATION OF TEETH
•The named branches of the superior (CN V2)
and inferior (CN V3) alveolar nerves give rise
to dental plexuses that supply the maxillary
and mandibular teeth.

81. INNERVATION OF TEETH

82. Teeth

83. Thank you for attention!