DIGESTIVE SYSTEM 1 Flashcards by humaira afzal

what is an alimentary tract?

A muscular tube, lined internally by an epithelium

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what epithelium lines the alimentary tract?

Epithelial type varies along length, depending upon function

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what are the structures of the oral cavity?

Teeth and periodontium (supporting tissue)
Tongue
Salivary glands

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what is the major functions of the oral cavity?

Ingestion + mechanical fragmentation of food

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what is the major histology of the oral cavity?

Lining of stratified squamous epithelium

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what is the structure of the tongue?

highly muscularised

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what is the function of the tongue?

Manipulates food for mastication

Taste

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what is the surface of the tongue covered by?

lingual papillae

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what does the lingual papillae include?

Filiform (most numerous)
Fungiform
Circumvallate
Foliate

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what are the structures of the transport passages?

Pharynx
Oesophagus
Anal canal

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what is the structure of the transport passages?

Simple muscular transport tubes
Lined with stratified squamous epithelium
Some mucous glands for lubrication

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what are the 3 layers of the oesophagus?

mucosa
muscular externa
adventitia

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what is the structure of the mucosa of the oesophagus?

Stratified squamous epithelium (above diaphragm)
Columnar epithelium (below diaphragm)
Well defined lamina propria + muscularis mucosae

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what is the structure of the muscular externa of the oesophagus?

Striated muscle (upper third)
Striated and smooth muscle (central section)
Smooth muscle (lower third)

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what is the structure of the adventitia of the oesophagus?

Layer of loose connective tissue

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what are the structure so the digestive tract?

Stomach
Small intestine (Duodenum, jejunum, ileum)
Large intestine (Caecum, appendix, colon, rectum)

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what is the histology of the tract?

Mucosa
Many epithelial types
Efficiency of absorption
Formation of complex glands

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what is the mucosa of the tract?

Inner layer surrounding tract – most variable component

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what are the epithelial types of the tract?

Absorptive

Secretory

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what is the efficiency of absorption of the tract?

Intrusions/folding of epithelium Villi/plicae

Inversions

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what are the 4 layers of the tract?

mucosa
submucosa
muscular externa
serosa

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what does the mucosa contain?

epithelium

lamina propria

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what is the epithelium of the mucosa?

Mainly columnar epithelial cells

Glandular secretions moisten surface

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what is the lamina propria?

Composed of loose CT
Contains small blood vessels, lymphatics, nerve fibres
Other specialist cells e.g. macrophages & lymphocytes

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what is the function of the submucosa?

Separates mucosa from underlying muscle layers

what does the submucosa contain?

More neural tissue Submucosal plexus (Meissner’s plexus) Regulates contractions + glandular secretions

what does the muscular externa contain?

smooth muscle Layers allow peristaltic contractions 2nd nerve plexus located between muscular layers - Myenteric (Auerbach’s) plexus

what are the 2 layers of smooth muscle in the muscularis externa?

Inner: circular layer Outer: longitudinal

how do the layers allow peristaltic contractions?

Circular layer is actually a compact spiral | Longitudinal layer is actually an elongated helix

what is the serosa+adventitia layer?

Covers muscularis | Delimits alimentary canal

what is the serosa?

When outermost layer lies adjacent to peritoneal cavity

what is the adventitia?

When connected to surrounding tissue

what is the serosa also known as?

visceral peritoneum

what is the function of the serosa?

CT with simple squamous epithelium | Lines majority of small and large intestine

where doesn't the serosa line?

part of duodenum + an area of the colon

where is no serosa found?

in oral cavity/ pharynx/ oesophagus/ rectus

what is the mesothelium?

the epithelial component of the serosa

what is the mesentary?

double layer of visceral peritoneum

what is the adventitia connected to and made of?

layer is connected to surrounding tissues | made of fibrous CT

what is the stomach?

Digestive organ + reservoir

what are the 4 anatomical regions of the stomach?

Cardia Fundus Corpus (body) Pylorus

what does the stomach contain?

mucosa | muscularis externa

what is the mucosa of the stomach?

Muscularis mucosae - circular and longitudinal muscle fibres

what are the 3 layers of the muscularis external of the stomach?

oblique, circular, longitudinal

what is the structure of the gastric mucosa of the stomach?

Columnar epithelium Rugae (gastric folds) Gastric pits

what is the rugae of the stomach?

Apparent when stomach is empty | Disappear when stomach is distended (full)

what are the gastric pits of the stomach?

Shallow surface depressions on surface

what are the tubular gastric glands of the stomach?

Open into gastric pits | Occupy entire mucosa

what is the function of the tubular gastric glands of the stomach?

Contain mucus producing cells | Mucus forms secretory sheath to protect against acid

what are the gastric glands (at cardia)?

Heavily branched | Mucus-producing glands

what are the principal glands(corpus-fundic) of the stomach?

Mucus neck cells

what are the chief cells in the principal glands of the stomach?

(zymogenic) – produces enzymes

what are the parietal cells in the principal glands of the stomach?

(oxyntic) – acid secreting

what are the enter-endocrine cells in the principal glands of the stomach?

stimulate secretion in other cells

what are the pyloric glands of the stomach?

More coiled than principal glands Endocrine cells more frequent No chief cells

what is the small intestine?

Most important digestive + absorptive functions occur here

what are the 3 sub-divisions of the small intestine?

Duodenum Jejunum Ileum

what does the mucosa of the small intestine contain?

``` plicae intestinal villi-entire intestinal mucosa microvilli on enterocytes tubular glands goblet cells muscularis mucosae ```

what is the function of the plicae of the small intestine?

Increase SA Permanent structures Absent from start of duodenum

what is the function of the intestinal villi of the small intestine?

Increase SA | Main cell type: enterocytes

what is the function of enterocytes?

have absorptive function

what is the function of themicrovilli on enterocytes of the small intestine?

increase SA

what does increasing the SA in the small intestine do?

improve efficiency of absorption

what is the function of Tubular glands (Crypts of Lieberkühn) in the small intestine?

from base of villi, through lamina propria to muscularis mucosae Secrete “intestinal juice” Paneth cells at base of crypt

what is the function of panted cells of the small intestine?

secretion + control of infection

what is the function of goblet cells in the small intestine?

secrete mucous

what is the muscularis mucosae in the small intestine?

Two layers + extend into villi

how does the regeneration of intestinal epithelia occur?

Epithelial cell turnover time: 1% per hour Undifferentiated stem cells at base of crypt Stem cells divide and ‘move up’ through crypt + villi

what does the submucosa of the small intestine contain?

glands only in the duodenum (Brunner’s glands)

what is the function of Brunner’s glands?

Secrete mucus to protect duodenal lumen

what does the muscularis externa of the small intestine contain?

Circular + longitudinal layers | Covered by serosa

what is the large intestine?

Frames small intestine | Reabsorption of water and inorganic salts

what are the 3 section of the large intestine?

Caecum (inc. appendix) Colon (ascending, transverse, descending, sigmoid) Rectum (inc. anal canal)

what does the mucosa of the large intestine contain?

``` smooth surface Crypts of Lieberkühn (longer than in SI) goblet cells (more numerous than in SI) Few endocrine cells Thin lamina propria Muscularis mucosa (2 layers) ```

what is the serosa of the large intestine?

Forms small pouches filled with adipose along large intestine

what is the muscularis externa of the large intestine?

Different appearance from SI | Longitudinal muscle layer forms 3 flattened strands (Taeniae coli)

what is the Taenia coli?

what is the Hausfrau coli?

sacculations of the colon