The Digestive System Lecture - PowerPoint Presentation

Slide1

The Digestive System

Lecture

11

Slide2

Ducts

The exocrine pancreatic secretion is discharged into the duodenum through

two pancreatic ducts

, the

main pancreatic

, and the

accessory pancreatic ducts

.

The

main

pancreatic duct

commences at the

tail

of the gland by the union of small ducts; in its course towards the duodenum it receives numerous tributaries from lobules.

The duct terminates by joining the bile duct at the

hepatopancreatic ampulla

.

1

Slide3

It opens into the second part of the duodenum at about its middle on the

major duodenal papilla

. Occasionally it may open independently into the duodenum.

An

accessory pancreatic duct

, which is much smaller than the main duct,

drains

the

front part of

the

head

of the pancreas and opens into the duodenum 2 cm proximal to the main duct on the minor duodenal papilla.

The accessory duct frequently communicates with the main duct.

2

Slide4

Common bile duct

Main pancreatic duct

Hepatopancreatic ampulla

Accessory

pancreatic

duct

3

Figure 16.

Pancreatic ducts

Slide5

Accessory pancreatic duct

Common bile duct

Major duodenal papilla

Main pancreatic duct

Head of pancreas

4

Figure 17.

Major and minor duodenal papillae

Slide6

Structure

The pancreas is

enclosed

by a

thin collagenous fibrous capsule

, which sends

septa

into it, separating the pancreatic

lobules

.

The exocrine component

Secretes 1500–3000 ml

of isomotic alkaline fluid per day, consists of closely packed secretory acini, which drain into a

highly branched duct system. Pancreatic acinus is composed of

several serous cells surrounding a lumen.

5

Slide7

The acinus cells

rest on a basement membrane

,

supported

by a

delicate sheath of reticular fibers

.

During secretory phase

the

lumen

is large and

distended with secretion

. 6

Slide8

Figure 18. Exocrine and endocrine pancreas (sectional view). Stain: hematoxyline and eosin. Low magnification.

serous acini and

zymogenis

cells

intercalated duct

pancreatic islet

interlobular connective

tissue septa

blood vessel

interlobular

connective tissue

interlobular duct

pancinian

corpuscle

blood vessel

centroacinar cell

capillaries

pancreatic islet

centroacinar cell

7

Slide9

Figure 19. Pancreatic islet.

Stain: hematoxyline and eosin. High magnification.

8

Slide10

Figure 20. Pancreatic islet (special preparation). Stain: Gomori

’

s chrome alum hematoxyline and phloxine. High magnification.

9

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intercalated

duct

connective

tissue

capsule

pancreatic islet

cenroacinar

ce

ll

secretory

acini

capillaries

Figure 21. Pancreatic endocrine (pancreatic islet) and exocrine region. Stain: peroxidase acid-schiff and hematoxiline. X 80.

10

Slide12

During the

resting phase

zymogen granules

accumulate in the cells, which enlarge and encroach on the lumen.

The

acenus

cells have

round

or

spherical

nucleus

. The

basal part of the cell shows cytoplasmic basophilia, indicative of the

protein synthesis involved in enzyme manufacture.

Acinus secretion contains water,

ions

, and

several proteases

.

Pancreatic secretion

is

controlled

mainly through two hormones–

secretin

and

cholecystokinin

.

11

Slide13

Both hormones

are

produced

by

enteroendocrine cells

of the small intestine (duodenum and jejunum).

Several acini join

an

intercalated duct lined

by

cuboidal

epithelium

.The initial

portions of intercalated ducts penetrate lumens of acini

. Nuclei, surrounded by a pale cytoplasm, belong to centroacinar cells

that constitute the intraacinar portion of the intercalated duct. 12A

Slide14

Slide15

12B

Slide16

12C

Slide17

Electron microscope shows that the cytoplasm of the a cinar cells contains numerous cisternae of

RER

, occupying the basal part of the cell, sugesting that these cells are involved with protein synthesis

.

Golgi complex

which occupies the apical pole of the nucleus is associated with several condensing vacules and numerous zymogen granules.

12D

Slide18

12E

Slide19

As compared with the

acinar

cell,

central cells

lack of

secretory granules

and

has very

scant

RER

.12F

Slide20

12G

Slide21

The

intercalated duct unite

to form larger ducts called

intralobular ducts

that, in turn,

unite

to form

larger interlobular ducts

line by

columnar epithelium

,

located within the connective tissue septa.

These ducts unite to form the main ducts

.12D

Slide22

The endocrine component:

Includes the

islets of Langerhans

, which

lie

mainly within the

lobules

(

intralobular

) but it may

occasionally be interlobular.

The islet appear as spherical masses or

cords of cells, which stain faintly with hematoxylin and

eosin, in contrast to the exocrine acini which stain deeply.

The islets are usually separated from the acini by a

thin reticular membrane

, but in places appear to be in direct continuity with acinar cells.

13

Slide23

Each islet has an

extensive blood supply

and the internal secretion from the cells passes directly into the blood stream.

Ultrastructural studies

reveal that the

islet cells

contain

small granules

that

concentrated

predominately in the

infranuclear region.

The majority of the

cells are β cells, known to secrete insulin, and

their granules have an oblong crystalline form. Of the remaining cells

, some are α cells that secrete glucagon, and have the more usual

spherical type of granule

.

14A

Slide24

14B

Slide25

14C

Slide26

Vessels and Nerves of Pancreas

The

superior pancreaticodudenal

branch of the

gastroduodenal artery

and

inferior pancreaticoduodenal

branch of the

superior mesenteric artery

supply

the

head of the pancreas (including the uncinate process

). The rest

of the pancreas is supplied by the splenic branch of the celiac trunk.

There is free anastomosis

between these arteries.

Veins

from the

head

drain into the

superior and inferior pancreaticodudenal veins

.

15

Slide27

The

rest

of the pancreas drains by the

splenic vein

.

Lymphatic vessels

from the pancreas pass to the

pancreaticosplenic nodes

(lie

along

the

superior border

of the pancreas) and aortic nodes

.

Sympathetic and parasympathetic nerves reach the gland from the coeliac plexus.

Pain fibers accompany the

sympathetic nerve

and enter the

central nervous system

via the

sympathetic trunk

.

16

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Most Important

I. Mouth (Oral cavity)

a. Bulk of the lips.

b. Boundaries of the vestibule

c. Boundaries of the mouth proper.

d. Communication of mouth proper.

e. Walls of mouth proper.

f. Lining epithelium.

17

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II. Salivary glands

Relations of parotid gland.

Relations of superficial part of submandibular gland.

Structures within the parotid gland.

Histology of salivary glands.

18

Slide30

III. Tongue

Papillae and their distribution.

Location of anterior 2/3 and posterior 1/3 of tongue.

Sulcus terminalis and foramen caecum.

Contents of taste buds.

Muscles of tongue: Action.

Motor and sensory supply of tongue.

 

IV. Soft palate:

Its muscle and nerve supply.

19

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V. Pharynx

a. Nasopharynx: Vertebral level of posterior wall; Tubal ridge; Communications, Level of pharyngeal isthmus; Extends.

b. Oropharynx: Palatoglossal and palatopha-ryngeal folds or arches; Communications; Extends.

c. Laryngopharynx: Extends; Communica-tions, Anterior wall.

d. Muscles of pharynx: Nerve supply, and actions.

20

Slide32

e. Gaps

between superior and middle constrictors; and between middle and inferior constrictors, and structures pass through these gaps.

f. Gaps between skull and upper border of superior constrictor, and structures fill this gap.

g. Histology of the wall of

pharynx.

21

Slide33

VI. Oesophagus

Relations of cervical and thoracic portions.

Level of deviation to the left.

Histology.

22

Slide34

VII. Peritoneum

Falciform ligament.

Median, medial, and lateral umblical ligaments.

Mesentery of small intestine.

Transverse mesocolon.

Sigmoid mesocolon.

Mesoapendix.

Lesser and greater omentum.

23

Slide35

Wall of lesser sac.

Innervation of parietal and visceral peritoneum.

Structure in the free (right) border of lesser omentum and the relations between them.

 

VIII. Stomac

h

Parts.

Relations and stomach bed.

Blood and nerve supply.

Lymphatic drainage.

24

Slide36

IX. Duodenum

Relations of each part.

Blood supply.

 

X. Jejunum and ileum

a. Plicae circulares, peyre's patches, and the differences between jejunum and ileum.

b. Differences in the mesentery.

c. Blood supply, arcades, and straight arteries.

25

Slide37

XI. Large intestine

Caecum: Location, relations, and blood supply.

Appendix: Location of its base; Differences in the position of its tip, and blood supply.

Ascending colon: Location, relations, and blood supply.

Transverse colon: Location and blood and nerve supply.

Descending colon: Location, relations and blood supply.

26

Slide38

Sigmoid

colon:

Its

termination and blood supply.

Rectum

: Location, relations, and blood supply

.

Anal canal: Location, relations, Histology, blood and nerve supply, internal and external hemorrhoids, and anal fissure.

27

Slide39

XII. Liver

Location.

Fissures.

Lobes.

Inferior (visceral) surface.

Boundaries of caudate and quadrate lobes and porta hepatis.

Histology of liver: Hepatocytes: Function of: Golgi complex, ESR, RER, Lysosomes, peroximase , and Hering's canal.

Functions of fat storing cells.

28

Slide40

h. Function of Kupffer cells.

XIII. Gall bladder and common bile duct

Parts.

Location of fundus. Histology.

 

IX. Common bile duct

Locations.

Histology.

Termination.

29

Slide41

Pancreas

Location

.

Relations

of head and body.

Its

relation to the transverse mesocolon.

Uncinate

process (part of what and

extends

In

which ligament the tail lies.

Ducts. Histology

of the exocrine portion.30