alimentary system tissues Flashcards by Joanna Reid

three key cell types in gi tract with function

modified epithelium = for secretion/ absorption/ protection
immune system = 70% of body immune system in gut
stem cells = regeneration

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features of epithelial lining of gut

secretes mucus for lubrication and protection
secreted hcl, hormones and enzymes for activity of digestive system
absorbs products of digestion
tight junctions form barrier

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features of gut for protection

highly developed immune system = GALT
diffuse immune cells = lymphocytes, macrophages
organised lymphoid structures = tonsils, appendix
paneth cells in small intestine
acidity of gastric juice

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features of stem cells

capable of renewing the entire cell population
maintain and renew cells constantly
self renew, proliferate and differentiate

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4 layers of the GI tract

mucosa
submucosa
muscularis
serosa

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mucosa features

epithelial lining
lamina propria
smooth muscle

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submucosa features

connective tissue with blood and lymph vessels, nerve plexus

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muscularis features

circular internal layer
nerve plexus
longitudinal external layer

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serosa features

connective tissue with mesothelium lining

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innervation of the gi tract

enteric nervous system

self sufficient but modulated by ANS

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two plexus and functions

meissners = submucosal (secretory function, mucosal movement, blood flow)
auerbachs = myenteric (between muscle layers, controls peristalsis )

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epithelium in oesophagus

stratified squamous

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function of oesophagus

muscular tube to move food along

folded in relaxed state

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what does the lamina propria contain in the oesophagus

mucus producing cells with secretory granules
to lubricate epithelium
houses GALT system

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other specialised cell in oesophagus mucosa

langerhans cell

antigen presenting cells, phagocytes

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oesophagus submucosa features

oesophageal glands with mucous and serous cells

mucus contains pepsinogen and lysozymes

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oesophagus muscularis and connective tissue features

muscularis has both smooth and skeletal muscle

connective tissue -> adventitia blends into surrounding connective tissue

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stomach function

processing food into thick acidic fluid = chyme

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what are rugae

lining of the stomach

folds of mucosa and sub mucosa

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4 regions of stomach

cardia, fundus, body, pylorus

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what is the funds filled with

gas

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stomach epithelium type

columnar

specialised invaginations into the mucosa

gastric pits
open into gastric glands
increase SA

6 cells type in stomach

surface epithelium 
mucous neck cells 
parietal
chief
regenerative stem
neuroendocrine

function of surface lining cells

thick layer of visible mucus secreter granules also secrete bicarbonate

function of mucus neck cells

more soluble mucus lubricates chyme protects cells from acid and enzymes

function of regenerative cells

replace all specialised cells | interspersed among neck cells

function of parietal cells

manufacture Hcl and gastric IF, extensive secreter network

function of chief cells

manufacture enzymes | short blunt microvilli

function of neuroendocrine cells

manufacture hormones open/closed type each type secretes one agent especially gastrin

lamina propria in stomach

thin | lots of capillaries, nerve fibres and lymphatics

muscularis layer features stomach

3 layers of smooth muscle | fibres in longitudinal, circular and oblique directions

adaptations of cardia region

short or simple branched glands with mucus secreting cells and a few parietal

adaptations of fundus region

branched tubular gastric glands (mucus neck, parietal, chief and endocrine)

adaptations of pylorus

shorter branched pyloric glands | secrete mucus, gastrin and somatostatin

plicae circulares in small intestine

transverse folds | particular prominent in jejunum

villi in small intestine

epithelial covered finger like protrusions of mucosa | glands of lieberkuhn at base

microvilli in small intestine

modifications of apical plasmalemma on villi of epithelial cells

crypts of lieberkuhn small intestine

invaginations into lamina propria | intestinal glands

main cell type in small intestine

enterocytes = columnar epithelium

enterocytes adaptations

absorptive cells with burst border | lamina propria forms core of villus, highly vascularised, contain lacteals

microvilli structure

contain cytoplasm and microfilaments actin filaments act as structural core structural core attached to plasma membrane by myosin and calmodulin

other cell types in small intestine r

``` goblet cells = produce mucus, protect neuroendocrine cells stem cells paneth cells = host defence cells (antimicrobial) ```

features of submucosa of duodenum

has Bruner's glands produce mucus, bicarbonate rich fluid to protect cells final breakdown of fats/carbs

lymphoid tissue of small intestine

GALT well developed

ileum lymphoid tissue specifics

peyers patchers = lymphocytes and antigen presenting cells | M cells = specialised epithelial cells that perform cellular surveillance of antigens

large intestine muscular coat

3 distinct strips | allow segments to contract independently = taenia coli

what does the large intestine lack

no folds no villi no nutrients absorbed

what are haustra

small segmental pouches on the surface of the large intestine

large intestine glands

deep glands lined by specialised columnar extensive goblet and absorptive cells, a few neuroendocrine

what are appendices epiploicae

small outpourings of adipose tissue in serous layer | help identify large intestine

colon specifics

lots of crypts, but no gland s | surface absorptive, goblet and regenerative cells

turnover rate of cells

complete regeneration from stem cells in crypts every 2-6days