alimentary system tissues Flashcards
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
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
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
features of stem cells
- capable of renewing the entire cell population
- maintain and renew cells constantly
- self renew, proliferate and differentiate
4 layers of the GI tract
mucosa
submucosa
muscularis
serosa
mucosa features
epithelial lining
lamina propria
smooth muscle
submucosa features
connective tissue with blood and lymph vessels, nerve plexus
muscularis features
circular internal layer
nerve plexus
longitudinal external layer
serosa features
connective tissue with mesothelium lining
innervation of the gi tract
enteric nervous system
self sufficient but modulated by ANS
two plexus and functions
meissners = submucosal (secretory function, mucosal movement, blood flow) auerbachs = myenteric (between muscle layers, controls peristalsis )
epithelium in oesophagus
stratified squamous
function of oesophagus
muscular tube to move food along
folded in relaxed state
what does the lamina propria contain in the oesophagus
mucus producing cells with secretory granules
to lubricate epithelium
houses GALT system
other specialised cell in oesophagus mucosa
langerhans cell
antigen presenting cells, phagocytes
oesophagus submucosa features
oesophageal glands with mucous and serous cells
mucus contains pepsinogen and lysozymes
oesophagus muscularis and connective tissue features
muscularis has both smooth and skeletal muscle
connective tissue -> adventitia blends into surrounding connective tissue
stomach function
processing food into thick acidic fluid = chyme
what are rugae
lining of the stomach
folds of mucosa and sub mucosa
4 regions of stomach
cardia, fundus, body, pylorus
what is the funds filled with
gas
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
