stomach Flashcards
Consists of the muscular tube from the mouth to the anus known as the:
Digestive tract
b.) Gastrointestinal tract
c.) Alimentary canal
a.) Liver/gall bladder
b.) Pancreas
c.) Teeth/tongue
d. Salivary glands
“Accessory” organs
Ingestion
b.) Mechanical digestion and propulsion
c.) Chemical digestion
d.) Secretion
e.) Absorption
f.) Defecation
g.) Protection from environment (from food/water)
Functions of GI:
a serous membrane that lines the abdomino-pelvic cavity
Peritoneum
Covers organs and projects into the
peritoneal cavity
Serosa (visceral peritoneum)
Continually produces peritoneal fluid to lubricate the surfaces and allows the serosa and parietal peritoneum to slide without friction
7L of fluid is secreted and reabsorbed per day
Serosa (visceral peritoneum)
lines the inner surface of the body wall
Parietal peritoneum
build of fluid in peritoneal cavity due to disease
Ascites
are double sheets of peritoneal membrane that connect the
parietal with the visceral peritoneum
Mesenteries
…. help stabilize the position of the attached organs and prevent
intestines from becoming entangled during digestive movement or body
positions
Mesenteries
what are the major mesenteries?
Lesser Omentum (First Mesentery) and Greater omentum (Second Mesentery)
ventral (anterior) surface of
the stomach, between the stomach and liver
Lesser Omentum (First Mesentery)
Stabilizes stomach and provides access point for blood vessels
for liver
Lesser Omentum (First Mesentery)
Stabilizes the position of the liver
Falciform ligament
between the abdominal
wall and intestines is another mesentery
Greater omentum (Second Mesentery)
- Acts as a padding and contains adipose tissue where further
fat can be stored
Greater omentum (Second Mesentery)
Mesentery proper is the main portion and is very thick. Covers
all but 10 inches of the small intestine
Mesentery helps to lock the duodenum and pancreas in place these organs are called _____ because they lie behind
the peritoneum rather than surround by it (this includes
all of the colon and rectum)
retroperitoneal
mucosa, submucosa, muscular layer,
serosa
Five major layers of the digestive tract
the innermost lining consisting of epithelium,
glandular secretions, a lamina propria of areolar tissue, and a muscularis mucosae
Mucosal Layer (mucosa)
The epithelium layer is ______ (oral, pharynx, esophagus, anal canal)
or _____ (stomach, small intestine and large intestine (colon))
stratified; columnar
a layer of areolar tissue containing blood vessels,
nerves, lymph, smooth muscle, and in some portions of the alimentary canal
secretory cells (ie. oral, pharynx, esophagus, stomach and Sm.Intestine)
Lamina propria
narrow sheet of smooth muscle with
both a circular layer (encircles the gastric tube) and parallel
layer (arranges parallel to the digestive tube) which allows the lumen
to change shape for movement
The muscularis mucosae
a layer of dense irregular connective tissue that binds the mucosa
to the muscular layer and contain blood vessels and lymph vessels and in some
portions exocrine glands that secrete buffers and enzymes
Submucosa
Contains a networks of nerves called the _________ – contains sensory neurons, PNS ganglion, and SNS fibers
Submucosal neural plexus
Consists primarily of smooth muscle
Muscular layer
______lies along the inner boarder of muscular layer.
Submucosal plexus
Contains an inner circular layer and an outer longitudinal layer – involved
in mechanical digestion
Muscular layer
Neurons of the _____ are primarily responsible for
movement of the muscles in the digestive tract
Enteric Nervous system
_______a network of parasympathetic ganglia, sensory neurons,
interneurons and sympathetic neurons found in between the
circular and longitudinal layer of the muscular layer
Fiber from the ANS innervate the myenteric plexus
In areas where the serosa is not covering the digestive organ, collagen
firmly attach the digestive tract to the that abdominal wall
adventitia
10 inch tube connecting the pharynx to the stomach moves ingested
material down toward the stomach
Esophagus
Mucosa contains stratified squamous cells
b.) Mucosa and submucosa packed into large folds
c.) Muscularis mucosa consists of irregular layer of smooth
muscle
d.) Submucosa contains esophageal glands
e.) First third of the esophagus contains skeletal muscle fibers
f.) Adventitia connects the esophagus to body wall
The esophagus will follow the basic layers of all the digestive system with a
few exceptions
First portion of the esophagus and last portion remain closed to prevent air from
entering in and to prevent stomach contents refluxing back into the esophagus
The upper portion called the upper esophageal sphincter
ii.) The lower portion called the lower esophageal sphincter (LES)
deglutition (swallowing) involves many different reflex arcs and
muscles - split into four phases
Ingestion
bolus of food pushes against hard plate and tongue
and other muscle push toward the soft palate forcing it into the
oropharynx and begins moving toward the stomach
Buccal phase
epiglottis closes and larynx elevates (preventing
food entering through the glottis into the trachea)
Pharyngeal phase
muscle contractions pushes contents into the
stomach (peristalsis)
Esophageal phase
will take over once food is actively pushed back into
the pharynx area (mediated by the swallowing center in the medulla oblongata)
The swallowing reflex
j-shaped organ which contains lesser curve forming the medial surface
and the greater curve forming the lateral surface
Stomach
the smallest region of the stomach and consists of the superior, and
medial portion of the stomach and contains mucous glands
Cardia
the region of the stomach that is superior to the junction between the
stomach and the esophagus
Fundus
area of the stomach consisting of the curve of the j-shaped and is the
largest portion
Body
forms the portion of the stomach between body and duodenum
and is much smaller – divided into pyloric antrum, pyloric canal, and pylorus
Pyloric part
surrounds the pylorus part and prevents duodenal
reflux and premature emptying
Pyloric sphincter
are fold within the stomach that allow for expansion
The rugae
contains simple columnar cells and together with the
mucous is called a secretory sheet – acts as a protection against acids and
enzymes
histology of stomach
Stomach has shallow depressions called _____ where specialized
cells are located
gastric pits
secret acids and enzymes - found in the fundus and
body
Gastric glands
Glands of the pyloric parts secret mucous and hormones
like
Gastrin
Gastric glands found in the gastric pits, are divided into ___ types
of cells: __- and ___ secrete 1500mL of
fluid each day
2 ; parietal cells and chief cells
secrete intrinsic factor for B12 absorption and
indirectly secrete HCl (pH of 1.5-2.0)
Parietal cells
HCl is produced via CO2 and H2O
Formation of HCL
-Forms carbonic acid via carbonic anhydrase (enzyme)
which dissociates and actively pumps H+ into the
stomach
-Chloride diffuses into the cells via the transporter
(pumps in Chloride and pumps Bicarbonate out
into blood (alkaline tide))
-Where Cl- diffuses into the lumen and combines to
form HCl
Formation of HCL
are most abundant cells near the base of gastric
glands. Secrete pepsinogen which changes to its active pepsin
via the acidic environment, used to digest incoming proteins
Chief cells
Babies secret renin and gastric lipase to aid in digestion of milk
Seven or more hormones are made by
enteroendocrine cells
produced by G-cells stimulates secretion by both parietal
and chief cells
Gastrin
produced by D-cells inhibits gastrin and
continuously secrete next to G-cells
Somatostatin
are involved with hunger where ghrelin
increases hunger and obestatin decreases hunger
Ghrelin and obestatin
begins in the mouth and continue in the stomach – as
stomach fluid increases and pH decreases protein digestion increase after
activation of pepsin
Chemical digestion
Gastric activity has a cephalic phase, gastric phase and intestinal phase
the sight, smell and taste of food begin activating
saliva and gastric juices via the vagus nerve to prepare for food entering the
stomach
Cephalic phase
begins with the arrival of food in the stomach and may
continue up to 3-4 hours after food enters
Gastric phase
Includes distention of the stomach, increasing the pH
and presence of undigested proteins which stimulates: HCl
production, gastrin to activate Chief and parietal cells,
and mixing waves which “churn” the contents
Gastric phase
effects the stomach and Sm. Intestine. Responsible
for controlling the rate of gastric emptying to ensure Sm.Intestine can
effectively complete the digestion process
Intestinal phase
Chyme enters sm. intestine and lipids, CHO’s, AA, and low
pH stimulate CCK, GIP, and Secretin which together inhibit
chief cells, parietal cells, peristalsis of the stomach and activate
various other mechanisms such as gall bladder secretions
Intestinal phase
a long muscular tube where most of the chemical digestion takes
place and 90% of all nutrients are absorbed. 20ft long
Small Intestine
contains permanently fixed circular folds (about 800) to increase
the surface for digestion
Small Intestine
Epithelial cells and underlying lamina propria of the circular folds form
small finger-like projections called_____ that also increase the surface area
villi
Epithelial cells contain ____which are cilia-like to trap
nutrients
microvilli
is found on the villi and contains microvilli and
mucus
Brush Border
Together the circular folds and villi increase surface area from
3300 cm2 (if the intestine was flatened) to 2 million cm2
In addition to blood vessels, and nerves which enter into each villi,
_____ are also present – gut based lymphatic vessels
lacteals
___lie deep in the crypts (base of the villi) and eject mucus to
cover brush boarder
Goblet cells
also found in crypts help to generate new cells (turnover rate
is 3-10 days
Stem cells
cells that release defensins and lysosomes to aid in
immunity at the gut level
Paneth cells
are specialized glands that release
additional mucus when chyme enters the duodenum and secrete urogastrone
to prevent excessive gastric acid secretion
Duodenal submucosal glands
Contains three segments – duodenum, jejunum, and the ileum
abut 10in long, receives pancreatic and gall bladder juices
to begin chemical digestion
Has few circular folds, and villi are small
Duodenum
about 8ft long is where most of the digestion and absorption
occurs
-Contains many circular folds and villi especially in the proximal
half with a decrease thereafter
Jejunum
11.5ft long and continues any digestion - leads to the
ileocecal valve which controls the flow of material into the cecum of the
colon
Ileum
The distal portion of the ileum lacks circular folds and is rather
filled with ______ – lymphoid tissues containing
many types of immune cells
Peyer’s patches
Digestion in the Sm.Intestin takes place after the stomach has released chyme
into the duodenum
Bile and enzymes from the pancreas are secreted to break down___
CHO’s, lipids and proteins
pH at the duodenum increase from 2 to upwards to 7-8 ____
due to glandular release of buffers and mucus (along with pancreatic buffers)
Chyme is the main signal for both neural and hormonal secretion
but PNS (rest and digest) is also highly involved
Segmentation and Peristalsis are engaged to properly mix and move the
chyme from
mouth to anus
Short reflexes are triggers by presence of
chyme or stretch receptors
“Controlling” neurons termed the _____ generate
myenteric reflexes (peristaltic and segmentation)
myenteric plexus
____ involve interneurons and motor neurons in the CNS and control glandular activity and large scale peristalsis
Long reflexes
Myenteric plexus also controls/activates
enteroendocrine cells
Gastrin, Secretin, Gastric Inhibitory Peptide (GIP), Cholecystokinin (CCK) Vasoactive Intestinal Polypeptide (VIP), Eterocrinin
Major Hormones of the duodenum aid in the proper balancing act of
digestion
secreted by G cells in duodenum when exposed to
incomplete digested proteins
- Functions - promoting increased stomach motility and
stimulating the production of gastric acids and enzymes
Gastrin
released in the duodenum when chyme enters
- Functions include activating pancreatic buffers to increase pH
and activate gallbladder to release bile, and reduce gastric
motility and secretions
Secretin
secreted when fats and
CHO’s enter duodenum and is accompanied by stimulation of
insulin release from pancreas
Gastric Inhibitory Peptide (GIP)
Secreted when chyme enters duodenum
- Function include accelerating all forms of digestive enzymes,
relaxes hepatopancreatic sphincter and contraction of
gallbladder to release additional pancreatic juices
and bile
> It also inhibits gastric activity and reduces hunger via
CNS activation
Cholecystokinin (CCK)
stimulates the
secretion of intestinal glands, dilates regional capillaries, and
inhibits acid production in stomach
Vasoactive Intestinal Polypeptide (VIP)
release when chyme enters the duodenum and
stimulates alkaline mucus via submucosal glands
Eterocrinin
____ takes on average 5 hours. Villi and mucus can move allowing
greater contact of particles with the intestinal cells and greater absorption in less
time and space
Absorption
is a large tube that has three segments depending on its location
around the abdomen. It is 5 ft long and is responsible for reabsorbing water,
formation and removal of wastes
Large Intestine
__include the cecum, colon and rectum
The three segments of the large intestine:
The first portion of large intestine connected to the ileum and is an expandable pouch – collects and stores materials from the ileum and begins “compaction”
Cecum
Contains the ___ – a muscular valve preventing backflow into
ileum
ileocecal valve
a small tube containing many lymph nodules and microbiota
Appendix
inflammation of appendix (ICVD versus
Appendicitis)
Appendicitis
the largest portion of the Large intestine containing series of pouches
called haustra which allow the colon to expand and elongate
Colon
a longitudinal band of smooth muscle that runs along the
outer surface and generates the haustra
Taeniae coli
___are small fatty sacs on the colon
Omental appendices
Colon contains four segments –
ascending, transverse and descending
begins at cecum and ends at the hepatic flexure (right
colon flexure)
Ascending
begins at hepatic flexure and ends at the splenic
flexure (left colon flexure)
Transverse
begins at splenic flexure and ends are
sigmoid colon
Descending
an “S” shaped structure 6in long between the
descending colon and rectum
Sigmoid
Histologically, the walls of the colon are thinner but the luminal diameter
is 3x as big as the sm.intestine
There are no villi but many goblet cells which secrete
mucus
histology of colon
Feces is about 75% percent water, 5% bacteria, and 20% epithelial
cells, waste, bile salts, unabsorbed nutrients and toxins
histology of colon
The majority of fermentation occurs here!
histology of colon
Urobilinogen and stercobilinogen from bilirubin generate the
color of feces
histology of colon
Ammonia, indole and skatole, and hydrogen sulfide generate
the odor of feces
histology of colon
the final portion of the large intestine and temporary storage site for
feces
Rectum
Small ____ are found in the anal canal and mark the border
between columnar and stratified squamous cells
anal columns
exit of the anal canal and contains an internal and external anal
sphincter (internal is smooth muscle under autonomic control and external is
skeletal under somatic/conscious control)
Anus
Veins in anal canal can become distended
(causing hemorrhoids)
takes place in the ascending an transverse colon
Haustral churning
Powerful peristaltic contractions called ____ move material
from the transverse through the rest of the colon and compacts into the
rectum
mass movements
Stretch receptors in rectum initiate the
defecation reflex
occurs as a result of the myenteric plexus and the
long reflex occurs via the parasympathetic innervation both
contributing to peristaltic contractions
the short reflex
Defecation can be withheld via the ___
when intra-rectal pressure builds up enough, the NS overrides
the voluntary response a bowel movement occurs
external voluntary muscles
are used for mechanical digestion, and to begin the chemical
digestion process via salivary enzymes
Mouth/Teeth
contain no melanin, no sweat glands, no sebum (can see blood
underneath which gives it its color)
Lips
Muscle used for the purpose of sensory analysis, secretion of mucins,
and manipulation of sound and food
Tongue
are living structures which have both blood and nerve supply to them
a.) Three layers (outer to inner): enamel, dentin, pulp connected with
collagen based gingiva and underlying periodontal ligaments (Removing
teeth needs to remove ligaments!)
Teeth
used for protection of teeth and mouth, enable speaking, and
secrete enzymes to help begin food digestion
Salivary glands
lies posterior to the stomach and acts as both an endocrine and
exocrine organ. It is an elongated organs about 6in and contains a head, body and
tail segment (a thin transparent capsule wraps around the entire organ)
Pancreas
____delivers the exocrine secretion of the pancreas into the duodenum after combining with the bile duct and empties into the duodenal papilla
Pancreatic duct
____which make and release insulin and glucagon (and
other hormones) represent 1% of the cells
Pancreatic islet cells
is the largest “visceral” organ weighing 3.3 pounds with tough fibrous cap
surrounding the entire organ and is found in the right hypochondriac region
Liver
separates right from left lobes of the liver and is used to
attached the liver to the back wall for stability
Falciform Ligament
thickened portion of the falciform ligament marking
the path of the umbilical vein
Round ligament
blood vessels and gall bladder branches converge at this point
into the liver
Porta Hepatis
the basic functional unit of the liver and are formed by
connective tissue (100,000 liver lobules in liver)
Liver lobules
liver cells: are arranged in plates around the central
veins in the middle of the lobule
Hepatocytes
Liver immune cells called _____ (Kupffer cells) line the
endothelial cells and are used to engulf debris and damaged cells – can even
store some minerals
stellate macrophages
(how blood enters the liver) Sinusoids from
small branches of the hepatic portal vein and hepatic artery proper are the major sources of blood.
Hepatic Portal System
The six portal triads are each corner of he hexagonal
shaped lobule and contain:
- Interlobular vein
- interlobular artery
- interlobular bile duct
Hepatic Portal System
Blood leaves the liver via the central vein to merge with the
inferior vena cava
____ can occur via damage to organ or a clot
preventing blood flow to liver and can cause issues with blood
proteins and even peritoneal bleeding causing distention
of the abdomen (ascites)
Portal hypertension
____liver makes and secretes bile into the bile canaliculi
extending outward away from the central vein
Bile Duct system
They continue and merge into bile ductulus to carry bile to nearest
portal area and end either the right or left bile ducts which
together form into the common hepatic duct and
eventually into the common bile duct
Bile Duct system
Metabolic regulations include:
- Carbohydrate metabolism
- Lipid metabolism
- Amino acid metabolism
- Waste removal
- Vitamin Storage
- Mineral storage
- Drug activation or inactivation
Physiology of the liver:
- Phagocytosis and antigen presentation
- Synthesis of plasma proteins
- Hormone activation/deactivation or removal
Ch24 – Digestion 15 - Antibody removal
- Toxin removal
Hematological Regulation
made mostly of water, with a small amount of ions,
bilirubin, cholesterol, bile salts and other lipids
Bile production
___- are made in hepatocyte from cholesterol and amino
acids
Bile salts
Used for emulsification
bile
Storage center for bile and is found underneath the liver connected
to the common hepatic duct
Gall Bladder
a band of skeletal muscle that wraps around the pancreatic and bile duct just as it enters the duodenum
Hepatopancreatic sphincter (sphincter of Oddi)
Bile is released under
CCK stimulation
crystallized cholesterol bile salts
Gallstones
