week 6 Flashcards
what is the gastrointestinal tract?
The continuous muscular
digestive tube that winds through
the body digesting and absorbing
foodstuffs.
what organs are in the gastrointestinal tract?
Organs include:
– mouth, pharynx, oesophagus,
stomach, small intestine
(duodenum, jejunum and ileum),
large intestine (ascending,
transverse, descending and sigmoid
colon), rectum and anus
Accessory digestive organs:
– teeth, tongue, salivary glands, liver,
gallbladder and pancreas
what are the functions of the gastrointestinal tract?
MIDAE
* Mastication (mouth) –
mechanical and chemical
breakdown
* Ingestion of food –
swallowing and propulsion
* Digestion – mechanical and
chemical breakdown of food
particles into pieces that can
pass through cell membranes
* Absorption – transfer of
nutrients from the gut to the
blood circulation
* Excretion – expulsion of
undigested material
Label the Gastrointestinal Tract
(alimentary canal)
What are the 4 layers of the GI tract?
- Mucosa lines the lumen; composed of:
– epithelium (different types in different locations but mostly
simple columnar epithelium and mucus-secreting cells)
– lamina propria (loose areolar connective tissue with
capillaries for nourishment and absorption)
– muscularis mucosae (smooth muscle that produces local
movements of mucosa) - Submucosa: dense connective tissue with glands,
blood/lymph vessels; also submucosal plexus (neural
network) – controls secretion - Smooth muscle/Muscularis Externa responsible for
segmentation and peristalsis; also contains myenteric
plexus (neural network) – controls motility - Serosa: visceral peritoneum
What are the 2 movements of the GI tract?
- Peristalsis and segmentation
What is peristalsis movement of the GI tract?
- Adjacent segments of GI tract organs
alternately contract and relax, which
moves food along the tract
distally.
What is segmentation movement of the GI tract?
- Nonadjacent segments of GI tract
organs alternately contract and relax,
moving the food forward then
backward. Food mixing occurs.
What is the peritoneum?
Serous epithelial membrane that covers the internal
walls of the abdominal cavity as well as the outer
surface of abdominal organs.
What 2 layers does the peritoneum consist of?
- parietal peritoneum – covers
internal abdominal walls - visceral peritoneum – covers
outer surface of abdominal
organs
What is Peritoneal cavity?
– space
between parietal and
visceral peritoneum
What are the 3 peritoneal folds?
- mesentery (suspends SI)
- mesocolon (suspends LI)
- greater omentum
Label this diagram
what is Mesentery and Mesocolon?
- two layers of visceral peritoneum against each other
What is the function of the mesentery and mesocolon?
- attach small and large intestines to the posterior abdominal wall
- allow freedom of movement in the abdominal cavity
- hold viscera in proper
relationship to each other - prevent the intestines from
becoming twisted and
tangled by changes in body
position and by its own
contractions - provides passage of blood
vessels and nerves that
supply digestive tract - contain lymph nodes and
vessels
What is the greater omentum?
- two layers of visceral peritoneum descend from stomach (anterior and posterior)
Function of the greater omentum
- pass in front of small
intestines, it then turns
upwards and backwards and
ascends to transverse colon - the two layers separate and
enclose the transverse colon - contains some adipose
tissue, which in obese
people accumulates in
considerable quantity - like an apron which covers
the intestines
Label this - Peritoneal Folds
Label this - Peritoneal Folds
Label this - Peritoneal Folds
Divisions of the GIT (embryologically)
– Foregut
* identified by (celiac trunk/celiac artery), which supplies foregut abdominal organs only
* mouth –> to first half of duodenum
– Midgut
* first half of duodenum –> to proximal half of large intestines
* identified by super mesenteric artery
- Hindgut
* distal half of large intestine –> to rectum
* identified by Inferior Mesenteric Artery
label image
label image
Mouth known as….
oral cavity
Main parts of mouth are
- Main parts:
– cheeks
– hard and soft palate
(form roof)
– uvula
– tongue
– teeth
what is the Oral cavity lined with …..
- Oral cavity is lined with stratified squamous epithelium which is kept moist by saliva
Label this diagram
label this mouth diagram
what is saliva produced by?
produced by salivary glands (parotid, submandibular
and sublingual)
what enzyme does saliva contain?
contains enzyme salivary amylase (starts
starch breakdown)
what is salivation triggered by
taste, smell, sight or thought of food
label this diagram
Salivation is stimulated by ….
the parasympathetic
nervous system via CN VII - facial nerve and CN IX -
glossopharyngeal nerve
label this diagram
what is teeth primarily composed of
dentin (similar to bone but composed of
calcified connective tissue)
what are the 3 parts of a tooth
crown, neck and root
what is dentin of the crown covered by
hard enamel
what is dentin of the root
covered by
softer cementum
what is inside the tooth?
pulp cavity and pulp (vessels and nerves)
where does the pulp cavity cavity extend into …
root canals
Alveolar processes of upper and
lower jaws are covered by….
gingiva
(gums)
Teeth are fixed to ……
Teeth are fixed to bony sockets of
the alveolar processes of the jaws
with many periodontal ligaments
label this diagram
what is Deciduous teeth
20 teeth that appear during 6-24 mnths
what is permanent teeth
32 teeth that appear at 6-12 years, this includes 3rd molars (wisdom) which appears from 17-25 years
What are the different types of teeth
Incisors (8 total)
- chisel-shaped for biting and
cutting
Canines (4 total)
- fang-like for tearing
Premolars (8 total)
- broad for crushing and grinding
Molars (12 total)
- broad for crushing and grinding
what is the tongue?
Muscular organ made of intrinsic muscles that change shape of
tongue; numerous extrinsic muscles alter tongue’s position
tongue function
Participates in food mixing during chewing, bolus formation and
initiation of swallowing; also essential for speech and taste
what does the sublingual glands produce
enzyme lingual lipase
what are the 2 digestions in the mouth ?
mechanical and chemical
what does the Tongue papillae house?
taste buds
What are the 3 types of taste buds?
– filiform: whitish, give the tongue
roughness and provide friction
– fungiform: reddish, scattered
over the tongue
– circumvallate (vallate): V-shaped
row in back of tongue
tongue also contains…
Tongue also contains lingual
tonsil (immune tissue)
label this diagram
what is mechanical digestion and its function?
Mechanical digestion (mastication or chewing)
– breaks food into smaller pieces
– mixes pieces of food with saliva
what is chemical digestion
refers to breakdown of
food through enzyme activity
what is the process of chemical digestion called and what is it?
the process is called hydrolysis – breakdown of
complex molecules into simpler ones with the
addition of a molecule of water
what is the main enzyme in the mouth and its function?
the main enzyme in the mouth is amylase – begins
starch digestion into simpler sugars
* this digestion stops in the stomach due to the high acidity
(low pH) of the stomach which neutralises amylase
what is the oesophagus?
Muscular tube that connects pharynx and stomach
where is the oesophagus located?
Located in the mediastinum
– anterior to the vertebral column
– posterior to the trachea
– posterior to the heart
where does oesophagus pass through?
- Passes through diaphragm at an
opening called the oesophageal
hiatus
what is the function of the oesophagus?
Function: transports food into the
stomach during swallowing.
– swallowing is aided by the presence of
saliva
– peristalsis moves the bolus stomach
label this diagram
what are the Four layers of the oesophagus?
– mucosa
– submucosa
– muscle layer
– outer connective tissue covering
(blending with surrounding
connective tissue)
function of Upper and lower oesophageal
muscular sphincters ?
control
passage of food; normally
closed, open during swallowing
what are the 5 stages of digestion?
What are the parts of the stomach?
Parts: cardia, fundus, body, pyloric antrum, pyloric canal and pylorus
(opening into duodenum with circular pyloric sphincter muscle)
What are the borders of the stomach?
Borders: lesser curvature (medial) and greater curvature (lateral)
Where is the stomach located?
Location: located under diaphragm in the left upper abdominal area
What are the stomach wall layers?
Stomach wall layers:
− mucosa - simple columnar epithelium; has large folds known as rugae that make the surface rough (to increase the mixing & mechanical breakdown effects)
− submucosa containing submucosal plexus
− smooth muscle arranged in several layers, containing myenteric plexus
− serosa – smooth visceral peritoneum
Label this diagram: stomach
Label this diagram: gastric mucosa
What is gastric mucosa composed of?
composed of simple columnar epithelium that folds inside the wall containing numerous gastric glands opening on mucosal surface via gastric pits
What do Surface Mucous and Mucous Neck Cells produce?
mucus and are the most numerous in the gastric mucosa
What do parietal cells produce?
hydrochloric acid (HCl) and intrinsic factor (protein required for absorption of vitamin B12)
What do chief cells produce?
digestive enzymes; pepsinogen and lipase
What are G cells, and they produce ?
produce hormone gastrin —> stimulates release of gastric juice and ↑ gastric motilit
Label this diagram of gastric mucosa
What is mechanical digestion achieved through?
achieved through peristaltic movements (mixing waves)
What does food turn into during mechanical digestion?
– food turned into thick soupy liquid called chyme
What 2 chemicals are involved in chemical digestion?
Hydrochloride acid and pepsin(also known as proteolytic enzyme)
during chemical digestion where does hydrochloric acid come from
– hydrochloric acid from parietal cells.
hydrochloric acid from parietal cells function
- kills microbes; denatures (unfolds) proteins from food
making enzymatic proteolysis easier; transforms
pepsinogen (inactive enzyme) into pepsin, inactivates
salivary amylase
pepsin (proteolytic enzyme) function
- breaks down protein chains into smaller peptide
fragments - most effective in the very acidic environment (pH=2)
what are the phases involved in Regulation of Gastric Secretion and Motility
Cephalic phase, gastric phase, Intestinal phase
what does the Cephalic phase start with
sight, smell, taste, thought of food
outcome of Cephalic phase
parasympathetic activation leads to stimulation of gastric
secretion and motility (via cranial nerve 10 – vagus)
what is Gastric phase activated by
activated via stretch receptors and chemoreceptors (monitor
pH) in the stomach after the food comes in
outcomes of gastric phase
outcomes: increased peristalsis (mixing), release of gastric –> increased gastric secretions
what is the Intestinal phase?
enterogastric reflex and hormones (enterogastrones -
secretin, cholecystokinin and vasoactive intestinal peptide)
decrease stomach secretions, motility and emptying
Gastric Motility and Emptying steps
Regulation of Gastric Emptying
- As chyme enters duodenum –>into intestinal phase
– Receptors respond to
stretch and chemical signals
– Enterogastric reflex occurs
(inhibits gastric motility) and
enterogastrones (inhibits
gastric acid production) - Carbohydrate-rich chyme
moves quickly through
duodenum - Fatty chyme remains in
duodenum 6 hours or
more
How long is the small interesting and location?
~6m long; from pyloric sphincter to
ileocaecal valve
function of small intestine
Major organ of digestion and
absorption
subdivisions of the small intestine
Subdivisions:
– Duodenum
* retroperitoneal = behind
parietal peritoneum
– Jejunum
* attached posteriorly by by
mesentery
– Ileum
* attached posteriorly
by mesentery
what is motility?
Motility: mostly segmentation with
intermittent peristalsis
label diagram of small intestine
what is the Duodenum?
1st part of Small intestine
size of duodenum
shortest part of the small intestine ~ 25 cm
location of duodenum
curves around head of pancreas
what does duodenum recieve
receives the bile duct
(from gall bladder and
liver) and main
pancreatic duct
(from pancreas)
what is the Brunner’s glands and its function
Brunner’s glands
secrete alkaline
mucus to neutralize
acidic chyme
label this diagram
what is Jejunum?
2nd part of SI (small intestine)
where is the jejunum located and size
– extends from
duodenum to ileum
– about 2.5 m long
what is the Ileum?
3rd part of SI (small intestine)
Location of ileum and size.
– extends from
jejunum to caecum
(1st part of LI)
– joins large intestine
at ileocaecal valve
– about 3.6 m long
label this diagram
what are the Vessels and Nerves of SI
- Superior mesenteric artery
-Veins - vagus nerve and sympathetics
what is Superior mesenteric artery (function and location)
Superior mesenteric artery (branch of the
abdominal aorta) brings oxygen-rich, nutrient poor blood supply
what do veins carry to SI?
Veins (carrying nutrient-rich, oxygen-poor
blood) drain into superior mesenteric veins –>
hepatic portal vein –> liver
what is vagus nerve and sympathetics
Vagus nerve (parasympathetic/rest and digest)
and sympathetics (fight or flight) from thoracic
splanchnic nerves serve small intestine
Label this diagram
label this diagram
what is Enterocytes?
Lined with simple columnar epithelium specialised for
absorption
what does small intestine contain(histology)
- contains numerous mucus-producing cells (Goblet cells)
- Contains Peyer’s patches which protect against bacteria
Structures that increase surface area of small intestine.
Structures that increase surface area:
– circular folds of mucosa (plicae circulares)
* permanent folds (~1 cm deep) that force chyme to slowly spiral
through lumen –> ^ nutrient absorption
– villi
* extensions (~1 mm high) of mucosa with capillary bed and
lymphatic vessels (lacteals) for absorption
– microvilli
* microscopic extensions of cell membrane on the upper surface
* microvilli form so-called brush border which contain some
digestive enzymes (for digesting carbohydrates and proteins)
Histology of Small Intestine diagram
when is Intestinal crypt epithelium renewed?
every 2-4 days
what cells do Intestinal Crypts contain?
Contain secretory cells
what do secretory cells in the intestinal crypts produce?
intestinal juice:
- 1- 2L secreted daily in response to distension or irritation of mucosa
- Slightly alkaline; isotonic with blood plasma
- Largely water; enzyme-poor (enzymes of SI only in brush
border); contains mucus
intestinal juice function
– Facilitates transport and absorption of nutrients
what are Enteroendocrine cells ?
-Enteroendocrine cells are specialized cells found in the gastrointestinal tract.
-They play a crucial role in regulating various digestive processes, including the secretion of hormones known as enterogastrones.
-Enterogastrones are hormones that primarily influence the functioning of the stomach and small intestine. T
Intraepithelial lymphocytes (IELs) function
– Release cytokines that kill infected cells
Paneth cells function
Secrete antimicrobial agents (defensins and lysozyme)
Stem cells divide to …..
produce crypt cells
label these diagrams
mechanical digestion in Small Intestine
– bile (from liver/gall
bladder), peristalsis and segmentation
chemical digestion in Small Intestine
– enzymes from pancreas and small intestine
label this diagram
what are the 7 steps of digestion n label diagram
Name the 3 major
branches of the
abdominal aorta that
supplies the GIT
Celiac trunk
Superior Mesenteric Artery
Inferior Mesenteric artery
Which peritoneal fold
suspends the jejunum
and ileum?
Mesentery
Where would you find
Chief cells? Name 1
enzyme they produce?
Stomach
Pepsinogen or lipase
B. Identify the
structures labelled i), ii)
and iii).
i) Parotid gland
ii) sublingual gland
iii) submandibular gland
Which cranial nerve
sends parasympathetic
fibres to the
Gastrointestinal tract?
Vagus nerve (CN10)
B The portal vein
contains oxygen poor
and nutrient rich blood
(TRUE/FALSE)
True
Name one structure in
the intestine that
increases the intestinal
surface area.
Either:
-Plicae Circulares (circular
folds)
- Villi
-Microvilli
What type of digestion occurs in the mouth?
Mechanical and chemical
And by what means does Mechanical and chemical processes occur?
Mechanical by chewing and tongue movements, and chemical by salivary
enzymes
What is the unidirectional movement of the oesophagus called?
Peristalsis
What type of digestion occurs in the stomach?
Mechanical and chemical
And by what means does mechanical and chemical processes occur?
Mechanical by stomach muscles and chemical by acids and enzymes
. Name and label the three muscle layers of the stomach wall. What is the importance of
having these three different layers?
Longitudinal, circular and oblique layers of muscularis externa.
Stomach can contract in many different directions enhancing the grinding effect and mechanical digestion
that occurs in the stomach.
Match the cell type with its function and location in the gastric pits
What type of digestion occurs in the small intestine?And by what means does these processes occur?
Mechanical and chemical. Mechanical by segmentation and
by bile and chemical by pancreatic and intestinal enzymes
Where in the GIT does nutrient absorption primarily occur?
Small intestine
Define the four layers of the Gastrointestinal Tract and list their functions:
- Mucosa: lines the lumen; composed of
epithelium (different types in different locations but mostly simple columnar epithelium and mucussecreting cells
lamina propria (loose areolar connective tissue with capillaries for nourishment and absorption)
muscularis mucosae (smooth muscle that produces local movements of mucosa) - Submucosa: dense connective tissue with glands, blood/lymph vessels; also
submucosal plexus (neural network) – controls secretion - Smooth muscle Smooth muscle responsible for segmentation and peristalsis;
also contains myenteric plexus (neural network) – controls motility - Serosa visceral peritoneum; attachment to mesentery (which carries blood
vessels and nerves)
What is the peritoneal cavity?
The space between the parietal
and visceral peritoneum
Which important structures travel
within the peritoneal folds?
Blood vessels, lymph vessels and nerves
Abdominal organs which are almost completely covered with peritoneum (such as the
stomach) are called? Give some examples.
Intraperitoneal; spleen, parts of the SI,
liver, tail of pancreas, stomach, transverse colon.
Abdominal organs which are only partially covered by peritoneum (usually on their
anterior surface e.g. kidney) are called?
? Retroperitoneal; pancreas (except tail),
ureters, colon (ascending and descending), kidneys, oesophagus and rectum.
What is the function of the greater omentum?
- Fat deposition: having varying
amounts of adipose tissue - Immune contribution: having milky spots of macrophage collections
- Infection and wound isolation: It may also physically limit the spread of
intraperitoneal infections. The greater omentum can often be found wrapped
around areas of infection and trauma.
Which gastrointestinal organs does the celiac trunk supply?
Inf. Oesophagus, stomach, 1st half of duodenum, liver and pancreas.
Which gastrointestinal organs does the superior mesenteric artery supply?
2nd half of duodenum, jejunum, ileum, ascending colon, 1st half of transverse colon.
Which gastrointestinal organs does the inferior mesenteric artery supply?
Second half of transverse colon, descending colon, sigmoid colon and rectum
What is the main organic molecule digested in the stomach?
Proteins are mainly digested in the stomach by hydrochloric acid and pepsin.
The propulsive function that occurs in the oesophagus is called __________.
peristalsis. The oesophagus uses peristalsis to move food toward the stomach.
Which hormone is produced by G cells that stimulates the release of gastric juices and increases gastric motility?
gastrin. G cells (which are located in gastric pits) produce the hormone gastrin, which stimulates the stomach.
Which of the following products does the stomach produce?
HCl and intrinsic factor. Parietal cells produce hydrochloric acid (HCl) and intrinsic factor (which is a protein required for absorption of vitamin B12).
Protective collections of lymphocytes and macrophages are found in __________.
Peyer’s patches
Which of the following cells produce pepsinogen?
chief cells
During swallowing, the bolus passes into the stomach from the oesophagus through the __________.
lower oesophageal sphincter. The bolus passes into the stomach from the oesophagus through the lower oesophageal sphincter, also known as the cardiac sphincter due to its close proximity to the heart.
What would be the effect of stripping the small intestines of their villi?
Decreased surface area for absorption would cause weight loss to occur.
label this
A: Tendinous intersection
B: Right External oblique muscle
C: Left Rectus abdominis muscle
D: umbilicus
label this
Specified Answer for: A
tongue
Specified Answer for: B
sublingual gland
Specified Answer for: C
submandibular gland
Specified Answer for: D
mandible
label this
a: left lobe of liver
b: greater omentum
c: spleen
d: body of stomach
label this
a: Duodenum
b: pylorus
c: rugae
d: greater ometnum
Starting from the deepest layer, which sequence below represents the correct layering of the wall of the GI tract?
mucosa, submucosa, muscularis externa, serosa
a:The mesentery
b:ileum
c: jejunum
__________ is the major means of propulsion in the digestive system.
Peristalsis
