DIGESTIVE SYS

Digestive Tract, Digestive glands

The digestive system consist of what:

Digestion of food (mechanical or chemical)
Absorption of digested substances (food)
Excretion of undigested materials (in anus in the form of feces)

What are the functions of the digestive system?

Digestion

involves the mechanical action of the digestive tract and the chemical action of substances and enzymes

Mechanical action

Cut food in smaller particles (in mouth)

Chemical action

Divide into smaller size with the use of substances and enzymes present

Mucosa
Submucosa
Muscularis
Serosa

What are the general 4 layers of the digestive tract?

Mucous epithelium, Lamina propria, Muscularis mucosae

What are the three layers of the mucosa?

Mucous epithelium

Located in the lumen of organ or colon

Visible / well-defined in esophagus up to anus

Not observable in oral cavity to pharynx

lamina propria of mucosa

Where the mucous epithelium is attached

Composed of loose connective tissue with blood vessels

Muscularis mucosae/ muscularis interna of mucosa

Smooth muscle tissue located in the outermost part of mucosa layer

Separates mucosa from submucosa

Submucosa

What layer of mucosa that consist of glands and blood vessels,

composed of dense irregular CT

Muscularis Enterna

Composed of muscularis layer and myenteric plexus

Muscularis layer

smooth muscle cells with 2 types of orientation
Two layers: Inner Circular, Outer Longitudinal

Myenteric plexus

Nerve between 2 layers of muscularis externa

Intramural plexus

submucosal + myenteric plexus; for contraction of muscle for peristalsis(move. bolus from one organ to another)

Serosa

Outermost layer of mucosa
Directly attached to visceral peritoneum
Loose connective tissue usually seen in peritoneum

Serosa

areas of digestive tract covered by peritoneum
\____ of small and large intestines is continuous with portions of mesentery that suspends the intestines and continuous with peritoneum

Covers organs that freely move inside a cavity

adventitia

no peritioneal covering

Esophagus is not suspended in a cavity but bound directly to adjacent structures

Covers organs that should be bound with the surrounding structures for support

2 regions of the oral cavity

1. vestibule
2. oral cavity proper

non-keratinized stratified squamous epithelium

what is the epithelium of the following:
Internal surface of lips, cheeks, soft palate & ventral surface of the tongue

keratinized stratified squamous epithelium

what is the epithelium of the following:
Hard palate to gums and vermillion zone of lips

vermilion zone

Hard palate to gums and vermillion zone of lips

labial glands
buccal glands
palatine salivary glands

types of glands in oral cavity

outer part of lips

keratinized stratified squamous is the epithelium of what part of the lips?

inside of lips

non-keratinized stratified squamous is the epithelium of what part of the lips?

stratified squamous epithelium

what is the epithelium of the tongue?

tongue

Muscular organ that plays an important role in
mastication, deglutition and speech

Histologically made up of skeletal muscle

lingual papillae

anterior portion of the tongue forms protrusions called?

circumvallate and foliate

what lingual papillae has/have taste buds in lateral surface

filiform papillae

determine the type of lingual papillae

Most numerous and found all over the dorsal surface of the tongue
● Highly keratinized stratified squamous

Fungiform papillae

determine the type of lingual papillae

Have flattened surface, broader and scattered among the filiform papillae
● Lightly keratinized stratified squamous
● Dense irregular CT

circumvallate papillae

determine the type of lingual papillae

Arranged along the sulcus terminalis
● Largest but least numerous
● Lightly keratinized stratified squamous (not as much
as fungiform) with taste buds

taste buds

Ovoid structures containing elongates gustatory (taste) cells, which turn over with a 7-10 day lifespan
○ Will be replaced with gustatory cells

taste pore

small opening on the surface of the epithelium

sodium ions

what ions present in salty tastant?

hydrogen ions

what ions present in sour tastant?

alkaloids and toxins

what ions present in bitter tastant?

carbohydrates

what ions present in sweet tastant?

amino acids

what ions present in umami/savory tastant?

pharnyx

funnel-shaped fibromuscular tuber

ciliated pseudostratified squamous
epithelium

epithelium of nasophraynx

nonkeratinized stratified squamous
epithelium

epithelium of orophraynx

nonkeratinized stratified squamous
epithelium and ciliated pseudostratified columnar epithelium

epithelium of laryngopharynx

laryngopharnyx

where nasopharynx and oropharynx overlaps

esophagus

Long muscular tube that serve as a passageway for food from pharynx to stomach

Gastro-Esophageal Junction

Simple columnar epithelium of stomach meets the nonkeratinized stratified squamous epithelium of esophagus

aka Z-line or Z-zone - Where esophageal cancer usually
occurs

Esophagus

nonkeratinized stratified squamous

Mixture of skeletal and smooth muscle, Depends on the location

upper part

adventitia is located at what part of the esophagus?

lower part

serosa located at what part of the esophagus?

inner mucosa

epithelium: nonkeratinized stratified squamous

composed of lamina propria and muscularis mucosa

lamina propria

directly attached to stratified squamous; consists of loose CT

muscularis mucosa

smooth muscle, serves as a barrier between mucosa and submucosa layer

submucosa

determine what layer of the esophagus is being described:

Blood vessels (the white oval/circular shaped) Glands consist of mucous cells

Mucous cells are dark because of the stain (prolonged duration of the tissue in the stain)

Muscularis interna is part of the mucosal layer

muscularis externa of esophagus

inner circular and outer longitudinal layers of skeletal muscle layer

stomach

A J-shaped hollow organ located in the left upper quadrant of the abdomen

chyme

what is an acidic semifluid mixture of food or bolus and gastric juice (secreted by gastric glands)

bolus

a small rounded mass of a substance, especially of chewed food at the moment of swallowing. it is in the digestive tract

rugae

longitudinal folds in the stomach

simple columnar with lamina propria (loose CT)

epithelium of mucosal layer in the stomach

muscularis interna

separates the mucosa and submucosa

3 orientation of muscularis externa in the stomach

outer longitudinal
middle circular
inner oblique

fundic glands

determine the type of gland in the stomach:

Most numerous and longest of the glands of the stomach

can be seen in the fundus

cardiac glands

determine the type of gland in the stomach:

least numerous

Cells present are the same in fundic-glands except that
mucus-secreting cells are most numerous

Gastric glands are tubular in shape while \___ \______are circular

pyloric gland

determine the type of gland in the stomach:

● Shorter but more coiled, Looks like sweat glands
● Most of the cells are mucus-secreting cells
● Same cells with the other

Oxyntic (parietal cells)
Zynogenic (Chief Cells)
Mucous Neck and Surface Mucous Cells
Stem Cells
Enteroendocrine Cells

5 types of cell in fundic glands

OZMuSuSe

Oxyntic (Parietal Cells)

cells in the fundic glands that are pyramidal in shape
with oval to round nucleus; produce HCl and
intrinsic factor

Zymogenic (Chief Cells)

cells in the fundic gland that are low columnar cells,
contain pepsinogen (inactive form of pepsin) and gastric lipase

Mucous Neck Cells and Surface Mucous
Cells

similar to zymogenic cells except for basally located, flattened nuclei; contain mucin

mucous

what is the acidic mucin

surface

what is the alkaline mucin

stem cell

cell in the fundic glands that renews the epithelial cell population
of the stomach

Enteroendocrine Cells (Enterochromaffin / Argentaffin cells)

Hormone producing cells in the fundic glands

G cell - release gastrin into the blood

small intestine

● Located between the stomach and large intestine
● Mainly responsible for absorption of nutrients from
digested food
● Approx. 3 to 5 meters

plicae circulares

valves of kerckring

- crescentic
or circular horizontal folds of the mucosa
○ Equivalent of rugae in the stomach

Duodenum
Jejunum
Ileum

3 parts of the small intestine

stem cells

determine the cell in the small intestine

Differentiate into different types of cells

enterocytes

determine the cell in the small intestine

Replace the absorptive cells of the lining epithelium

● Absorption function of small
intestine

goblet cells

determine the cell in the small intestine

● Secretory in function

● Mature enterocytes

Paneth cells

determine the cell in the small intestine;

● Large pyramidal cells
● Capable of phagocytosis

enteroendocrine cells

determine the cell in the small intestine

Releases hormone secretions

duodenum

the only segment of the small intestine that has a gland located in the submucosa layer; the rest of the glands is located in the mucosa layer

brunner's gland

neutralizes acid in stomach

Once duodenum receives bolus (coming from the stomach), it neutralizes the bolus

meisnner's plexus

nerves that are responsible for the contraction of small intestine

Auerbach's plexus

what plexus functions for contraction aside from meissner's plexus

Crypts of Lieberkuhn

part of ileum that has paneth cells
Lamina propria (loose CT)

large intestine

● Most distal segment of digestive tract

Water and remaining nutrients are absorbed and the
remaining waste material is stored as feces before being
removed by defecation

● Epithelium: Simple columnar epithelium

● Composed of:
○ Ascending Colon
○ Transverse Colon
○ Descending Colon
○ Appendix

False. Longer and Bigger

T/F

Crypts of Lieberkuhn of the large intestine is shorter and smaller than the small intestine

VERMIFORM APPENDIX

● A short narrow and wormlike tubular evagination of the cecum

● Consists mainly of tall columnar cells with microvilli

● Heavily infiltrated by GALT

mucosa (of vermiform appendix)

what layer of vermiform appendix that is simple columnar epithelium

has Crypts of Lieberkühn

heavily infiltrated by GALT --mixture of loose connective tissue and lymphoid tissue

rectum

○ Act as a temporary storage for feces

○ Simple columnar epitheliums

anus

An opening at the far end of the digestive tract
which stool leaves the body

Non-keratinized stratified squamous

Rectal Columns of Morgagni

○ Longitudinal mucosal folds in anal canal
○ The region where the rectum and anus meets
○ Stratified Squamous Epithelium

salivary glands

Classified into MINOR and MAJOR Salivary glands

Collective secretion of the salivary gland is called Saliva

1.5 L of saliva per day

lingual lipase
ptyalin or salivary amylase

saliva contains what digestive enzymes

glandular epithelium

parenchyma of major salivary glands

Secretory units in the form of ACINI (ALVEOLI)

connective tissue

stroma of major salivary glands

Capsule: envelopes the gland
○ Septae: divides the glands into lobes

Crescents of Giannuzzi or Demilunes of Heidenhain

○ Cellular formations in the shape of a half-moon

○ Contain serous cells at the distal end of
mucous tubuloalveolar secretory unit

Myoepithelial cells

○ Flattened, contractile stellate cells found in the
mucous or mixed acinus

○ Function is to help the secretory units to eject their secretions

intercalated ducts

Segment of duct system (of the salivary glands) that directly drains an acinus

Simple squamous to low cuboidal

striated/secretory duct

o type of intraolublar duct that is Formed by the union of intercalated ducts
o Simple cuboidal or columnar