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By the end of this section, you will be able to:
  • Label on a diagram the four main regions of the stomach, its curvatures, and its sphincter
  • Identify the four main types of secreting cells in gastric glands, and their important products
  • Explain why the stomach does not digest itself
  • Describe the mechanical and chemical digestion of food entering the stomach

Although a minimal amount of carbohydrate digestion occurs in the mouth, chemical digestion really gets underway in the stomach. An expansion of the alimentary canal that lies immediately inferior to the esophagus, the stomach links the esophagus to the first part of the small intestine (the duodenum) and is relatively fixed in place at its esophageal and duodenal ends. In between, however, it can be a highly active structure, contracting and continually changing position and size. These contractions provide mechanical assistance to digestion. The empty stomach is only about the size of your fist, but can stretch to hold as much as 4 liters of food and fluid, or more than 75 times its empty volume, and then return to its resting size when empty. Although you might think that the size of a person’s stomach is related to how much food that individual consumes, body weight does not correlate with stomach size. Rather, when you eat greater quantities of food—such as at holiday dinner—you stretch the stomach more than when you eat less.

Popular culture tends to refer to the stomach as the location where all digestion takes place. Of course, this is not true. An important function of the stomach is to serve as a temporary holding chamber. You can ingest a meal far more quickly than it can be digested and absorbed by the small intestine. Thus, the stomach holds food and parses only small amounts into the small intestine at a time. Foods are not processed in the order they are eaten; rather, they are mixed together with digestive juices in the stomach until they are converted into chyme, which is released into the small intestine.

As you will see in the sections that follow, the stomach plays several important roles in chemical digestion, including the continued digestion of carbohydrates and the initial digestion of proteins and triglycerides. Little if any nutrient absorption occurs in the stomach, with the exception of the negligible amount of nutrients in alcohol.

Structure

There are four main regions in the stomach    : the cardia, fundus, body, and pylorus ( [link] ). The cardia    (or cardiac region) is the point where the esophagus connects to the stomach and through which food passes into the stomach. Located inferior to the diaphragm, above and to the left of the cardia, is the dome-shaped fundus    . Below the fundus is the body    , the main part of the stomach. The funnel-shaped pylorus    connects the stomach to the duodenum. The wider end of the funnel, the pyloric antrum    , connects to the body of the stomach. The narrower end is called the pyloric canal    , which connects to the duodenum. The smooth muscle pyloric sphincter    is located at this latter point of connection and controls stomach emptying. In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a ruga    .

Questions & Answers

how to identify tissues cells under a microscope
Carla Reply
any advice on how to identify tissue cells under a microscope?
Carla
What is homeostasis
Haji Reply
ability of living organisms to adjust it internal environment to maintain a stable equilibrium
famuyiwa
how to identify tissues cells under a microscope
Carla
what is the anatomy
aamina Reply
anatomy is the branch of science concerned with the bodily structure of humans animals and other living organisms, especially as revealed by dissection and the separation of parts.
Misikir
what are silhouettes
Magret Reply
is dis Medical term?
Preity
yes
Magret
but I don't know what it means
Magret
silhouette outline of a figure. The sharpness of the silhouette is a function of the shape, size and density of the object. This is most marked in radiography. basketball-shaped silhouette the enlarged cardiac outline seen in the dorsal-ventral view of the thorax in a dog with chronic pericardial
Callisto
Homeostasis
Haji
it's the first stage of wound healing that involves vasoconstriction platelet plug formation and blood clotting
famuyiwa
Levels of complexity
julie
sorry that was fast hemostasis
famuyiwa
Kkkk
julie
Anti there is homeostasis and haemostasis
julie
yes , homeostasis is the abiltity of a living organism to adjust it environment to maintain a stable equilibrium
famuyiwa
Thank you Alice, how about Haemostasis?
Christina
why are postsynaptic ganglionic neurons unmyelinated
Callie Reply
Postganglionic motor neurons are unmyelinated because the lack myelin sheath. The myelin sheath on the peripheral nervous system is composed of Schwann cells wrapped around the axon inside the endoneurium.
Carmelo
they lack*
Carmelo
Postganglionic (and preganglionic) motor neurons belong to the division of the autonomic nervous system. In contrast, the somatic nervous system contains only one long thick myelinated somatic presynaptic motor neuron.
Carmelo
anatomy defination in urdu
Atif Reply
human body largest organ.....
jasveer Reply
liver
JOY
liver
Lem
Skin
amen
lungs
Zamiir
liver and skin
Marina
skin
brian
by mass is liver but externally is de skin
Kumsah
all answers Are correct
brian
no
Rehman
liver is the largest gland of the body but skin is the largest organ of the body
Rehman
so please what is the answer now
Marina
afcous skin.because difference between Gland and organ
Safiya
Only the skin
Williams
The largest organ is the skin and the liver is a gland
Williams
skin is the largest organ of the body
Denis
liver
julie
it's the skin
trinna
skin 100%
Mallikharjun
largest organ- liver largest system- Skin
Shahriar
largest organ is skin because it covers the rest of the organs
Syed
liver right answers
nisha
liver
Justine
skin
Areej
liver is largest gland
Areej
skin is largest organ liver is largest gland femur is largest bone thyroid gland is largest endocrine gland seratus muscle is largest muscle
Tanveer
sciatic nerve is largest nerve
Tanveer
portal vein is largest vein
Tanveer
GIT is largest tube in body
Tanveer
explain about cerebrum cereblum and pons medulla
Tanveer
Nervous system anotomy and physiology
Tanveer
skin is the human body's largest organ
Kimbley
@Tanveer, the cerebrum consists of the cerebral cortex, corpus callosum, hippocampus, and basal ganglia. The cerebellum is located inferior to the occipital lobe. The pons and medulla are part of the lower brainstem.
Carmelo
The cerebral cortex are divided into 4 lobes and control functions such as: thinking, learning, speech, sensory perception, motor functions, hearing and vision, etc. The cerebral cortex is mainly present only in mammals due to evolution. The hippocampus plays a main role in memory formation.
Carmelo
The cerebellum works together with the motor cortex and other parts of the brain to coordinate and fine tune muscular activity. The pons and medulla control autonomic functions such as: sleep, respiration, swallowing, vomiting, heart rate, vasomotor control and more other things.
Carmelo
skin hai friend
Tilak
what is the biliary tract
famuyiwa
The biliary tract involves the liver, gallbladder, and bile duct. Certain liver cells (hepatocytes) synthesize bile salts derived from cholesterol in response to Secretin hormone. The gallbladder stores the bile. Gallbladder releases bile to the bile duct in response to Cholecystokinin hormone.
Carmelo
The role of bile is to emulsify fats so that they can be easily broken down and absorbed by the enterocytes into the lacteal vessels.
Carmelo
what is the difference between negative feedback loop and positive feedback loop
famuyiwa
what is cholesterol
Kay
unsaturated fats
famuyiwa
so what is the main purpose of anomaly
Kay
Cholesterol is a waxy substance your body uses to protect nerves, make cell tissues, and produce certain hormones.
Favour
Cholesterol is a type of lipid and it is a nonpolar molecule. The molecule is mainly composed of hydrocarbon chains. Cholesterol is synthesized in the smooth endoplasmic reticulum in eukaryotic cells, and is the main building block material for steroids, Vit D, and bile salts.
Carmelo
Negative feedback loop reverses any change back to its set point. For ex, when your internal body temperature rises above 98.6 F, your hypothalamus triggers your dermal blood vessels to dilate and activate sweat glands through sympathetic motor nerves so you can sweat and cool off back to 98.6 F.
Carmelo
Positive feedback loop amplifies a change. For ex, during labor, oxytocin is released continuously in a positive feedback loop from the posterior pituitary gland to stimulate contraction of the myometrium so the baby can come out.
Carmelo
define homeostasis and explain it's importants
Adusei Reply
define the important life processes of humans
Adusei
how the bone marrow transplantation is done?
Tanveer
what is homeostasis
julie Reply
internal temperature of body
Sanket
Homeostasis is the internal constancy in which your body tries to maintain for optimal cellular functioning. For example, your body tries to maintain an internal body temperature of about 98.6F for optimal functioning of your body.
Carmelo
If a prolonged lost of homeostasis occurs, death of the organism will be the outcome.
Carmelo
Another example of homeostasis is that your body tries to maintain a specific blood sugar level, so that your cells can undergo constant cellular respiration and keep you alive.
Carmelo
homeostasis is the fairly constant internal changes of an environment (your internal environment).The temperature of a body must be kept between the range of 37.5°c
raphael
which tissue is more sensitive
Rit Reply
to what?
Lari
myasthenia gravis?
Selva
Myasthenia gravis is an autoimmune disease in which your own antibodies (produced by plasma cells) attack and inhibit nicotinic receptors at the neuromuscular junction.
Carmelo
As a result, acetylcholine will not bind to nicotinic receptors and now action potential is produced on the sarcolema. If no AP is produce, then there is no contraction of the muscle. For a long period of time, this will result in atrophy and muscle weakness.
Carmelo
and no action potential*
Carmelo
explain types of hypertension
Juli Reply
What is bulbar paralysis?
Roshni Reply
how can make penis larger
Marwat Reply
what is the stimuli initiates the control of erythropoiesis?
Ok Reply
oxygen
Liyungu
Erythropoietin, a hormone synthesized and released by the kidneys stimulate erythropoiesis in red bone marrow. When an Individual loses blood (hemorrhage) and the concentration of RBCs or oxygen decreases, erythropoitein will be released.
Carmelo
how lymph is from
Hafsa Reply
Lymph is essentially interstitial fluid that ends up in the lymphatic vessels that didn't go back into the venules. Lymph is composed of the same components as your blood plasma which contains water, solutes, oxygen, CO2, foreign particles such as toxins, bacteria and viruses.
Carmelo
what is the cause of twins
Clarus
The cause of identical twins is when a single fertilized egg undergo mitosis (splits in two) . As a result, both eggs now have the same genetic information, therefore producing two identical twins.
Carmelo
Different twins (fraternal) occurs when two different eggs are ovulated and two different sperm fertilize each egg. As a result, fraternal twins are not genetically identical and can even be opposite sex.
Carmelo
Fraternal twins occurs when two different eggs are ovulated and two different sperm fertilize each egg. As a result, fraternal twins are not genetically identical and can even be opposite sex.
Carmelo
If two eggs are ovulated during ovulation, and two different sperms fertilize each egg then fraternal twins will occur. Fraternal twins are not generically identical and can even be opposite sex.
Carmelo
Fraternal twins occurs when two different eggs are ovulated and two different sperm fertilize each egg. As a result, fraternal twins are not genetically identical and can even be opposite sex.
Carmelo
how structure and function relate to each other?
Garmai
This is a very important rule in Anatomy and Physiology. The structure of a cell, tissue, or organ will tell you a lot about it's function.
Carmelo
For example, simple columnar cells (enterocytes) in the villus present in the duodenum of the small intestine contain microvilli. Microvilli are finger like projections of the cell membrane (produce by the cytoskeleton)that increase the surface area for absorption of nutrients into the enterocytes.
Carmelo
The main role of these enterocytes is to absorb. Therefore, having Microvilli as a structure relates to its function.
Carmelo
@ Carmelo thanks for the answer.
Garmai
welcome
Carmelo
what is the difference between negative feedback loop and positive feedback loop
famuyiwa

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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