abdomen Flashcards
how does the digestive system contribute to homeostasis
The digestive system contributes to homeostasis by breaking down food into forms that can be absorbed and used by body cells .
Homeostasis: An equilibrium in the body of nutrients.
what does the food we eat contain and why are they essential to our body
The food we eat contains a variety of nutrients that are essential to our body.
These are needed to build new tissues, repair damaged ones and sustain necessary chemical reactions.
why does the food we eat need to be broken down
the food we eat consists of molecules that are too large to be used by body cells.
Therefore, foods must be broken down into molecules that are small enough to cross the membranes ofcells.
what are the two groups of organs that form the digestive system
There are two groups of organs that form the digestive system:
Gastrointestinal tract (GIT)
Accessory digestive organs
anatomy and regions
right hypochondriac region
right lumbar region
right iliac region
middle - midclavicular plane
epigastric region
umbilical region
hypogastric region
left hypochondriac region
left lumbar region
left iliac region
where is the midclavicular planes found
where is the subcostal plane found
where is the transtubercular plane found
what are the 4 quadrants in the abdominal region
right upper quadrant
right lower quadrant
left upper quadrant
left lower quadrant
Alternatively, the abdomen can be descriptively divided intofour quadrants divided by:
Themedian sagittal plane
Thesubcostal plane
In clinical context, you may see a radiology request for:“RUQ pain - ?cause”
label where these are found
diaphragm
stomach
liver
gallbladder
stomach
transverse colon of large intestine
descending colon of large intestine
ascending colon of large intestine
small intestine
cecum
appendix
initial part of sigmoid colon
urinary bladder
label where these are found
diaphragm
stomach
liver
gallbladder
stomach
transverse colon of large intestine
descending colon of large intestine
ascending colon of large intestine
small intestine
cecum
appendix
initial part of sigmoid colon
urinary bladder
what are the components of the alimentary tube in the digestive system
Alimentary Tube
Oral cavity
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine
Rectum
what are the components of the Accessory Organs
in the digestive system
Accessory Organs
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
label these on a diagram
mouth
partoid gland - salivary gland
pharynx
teeth
tongue
esophagus
liver
stomach
gallbladder
pancreas
duodenum
ascending colon transverse colon
descending colon
ileum
cecum
appendix
sigmoid colon
rectum
anus
alimentary tract wall histology
what are the layers in the alimentary tract layers
mucosa
sub - mucosa
muscularis
serosa
what are the characteristics of mucosa
Inner most layer
has 3 essential functions
Secretion – digestive enzymes, mucous
Absorption – digestive products
Protection – against bacteria
the layers of it are
epithelium
lamina propia
muscularis mucosae
Epithelium
- Stratified (layers) squamous cells are in the mouth, pharynx, oesophagus and anal canal (Protect)
- Simple columnar cells are in the stomach and intestine (Absorption and Secretion)
Lamina Propria
- Contains the blood and lymphatic vessels where nutrients are absorbed
- Contains Mucosa-Associated Lymphoid Tissue (MALT) which composes of lymphocytes and macrophages
Muscularis Mucosae
- Smooth muscle fibres that creates small folds to increase surface area
what are the characteristics of submucosa
Areolar connective tissue containing:
Submucosal plexus (plexus of Meissner) – a portion of the ENS (Enteric Nervous System)
- Sensory enteric neurons
- Motor enteric neurons
- Parasympathetic postganglionic fibres
- Sympathetic postganglionic fibres
- Arterial and venous blood supply (The Submucosa is highly vascularised)
- Submucosal glands
- Lymphatic tissue
what are the characteristics of submucosa
Areolar connective tissue containing:
Submucosal plexus (plexus of Meissner) – a portion of the ENS (Enteric Nervous System)
- Sensory enteric neurons
- Motor enteric neurons
- Parasympathetic postganglionic fibres
- Sympathetic postganglionic fibres
- Arterial and venous blood supply (The Submucosa is highly vascularised)
- Submucosal glands
- Lymphatic tissue
what are the characteristics of Muscularis
Skeletal muscles:
- Found in the mouth, pharynx, (superior and middle) oesophagus and forms the external anal sphincter
- Voluntary swallowing/movements
Smooth muscles:
- Found in the remainder of the GI tract not listed above i.e. lower oesophagus to the sigmoid colon/rectum
- Mostly two layers –
- Inner layer is circular fibers (thickened areas form sphincters)
- Outer layer is longitudinal fibers
Second plexus of the ENS - Myenteric plexus (plexus of Auerbach)
- It mostly controls GIT tract motility (frequency and strength of contractions)
- It contains:
Enteric neurons
Parasympathic ganglia
Parasympathic postganglionic fibers
Sympathic postganglionic fibers
what are the characteristics of serosa
Serous membrane composed of connective tissue and simple squamous epithelium
Superficial layer of the GI Tract
- Adventitia – covers the oesophagus only and comprises of areolar connective tissue
- Visceral peritoneum – below the level of the diaphragm
- Consists of a layer of simple squamous mesothelium with an underlying supporting layer of connective tissue
what are the characteristics of Peritoneum
The peritoneum is the largest serous membrane in the body
Parietal peritoneum lines the wall of the abdominal cavity
The visceral peritoneum lines some of the organs in GIT and is the serosa layer
The slim space in between these is the peritoneal cavity and is filled withserous fluid
- In certain diseases the cavity fills with several litres of fluid distending the abdomen - Ascites
Peritonitis
- Severe (life-threatening) – from perforation or surgical intervention introducing infectious microbes
- Non-life threatening (still very painful) - rubbing together of inflamed surfaces
The GIT nerve supply
The GIT and its related accessory organs are supplied from both divisions of the autonomic nervous system: the parasympathetic and sympathetic
The action of each division is generally opposite to the other and they both act according to body needs. The activity of the parasympathetic division is increased when digestion is required.
The parasympathetic supply of the GIT is by one pair of the vagus nerves and their effects are:
- Increased muscular activity – especially for peristalsis.
- Increased glandular secretion (Waugh and Grant 2014).
The sympathetic supply of the GIT is by numerous nerves from the spinal cord from the thoracic and lumbar regions, and their effects are:
- Decreased muscular activity – especially peristalsis.
- Decreased glandular secretion (Waugh and Grant 2014).
what are the GI tract’s functions
Ingestion
The intake of food and liquids into the mouth
Propulsion
The process of moving food through the alimentary canal: Swallowing (voluntary) and peristalsis (involuntary)
Mechanical breakdown
The process of increasing the surface area of ingested food physically to prepare it for digestion by enzymes: Chewing, Churning and Segmentation
Chemical digestion
The process of catalysts breaking down complex food molecules into their chemical building blocks
Absorption
The passage of digested end products (plus vitamins, minerals, and water) from the lumen of the GIT
Defecation
Expelling waste and indigestible foods from the body
functions of the mouth
Oral (Buccal) cavityFunctions:
- Ingestion
- Propulsion (Swallowing/deglutition)
- Mechanical and chemical breakdown - Digestion
Anatomy and Physiology:
- Stratified squamous epithelium
- Skeletal muscles and bone bind the region
- Accessory digestive organs perform most functions
The functions of the mouth:
- It analyses material before swallowing
- It mechanically processes material through the action of teeth, tongue, and palates
- it lubricates material by mixing it with mucus and saliva
- It begins the digestion of carbohydrates with help of salivary enzymes (amylase)
characteristics of the mouth
The mouth is formed by cheeks, hard palate, soft palate and the tongue.
The cheeks and lateral walls of the mouth are continuous with the lips
The lips are fleshy folds around the opening of the mouth
They are muscle covered by skin externally
The hard and soft palate form the roof of the mouth
- Anteriorly is the hard palate formed by bone
- Posteriorly is the soft palate which is formed of muscle
- Extending posterior-inferiorly from the soft palate is the uvula
what are the functions of teeth
Accessory digestion organs
- Deciduous (primary) dentition erupt from 6-32 months
- Deciduous teeth are lost from 6-12 years
- Permanent (secondary) dentition erupt from 7-25 years
- Enamel hardest substance in the body
- Dentin harder than bone
- Periodontal ligament anchors teeth and absorbs shock
- Mastication (to chew)
Cutting
Tear and shred
Crush and grind
Tongue
Accessory digestive organ composed of skeletal muscle held together by connective tissue
Gustation (taste) is detected by most papillae found on the tongue
- Foliate papillae (most)
- Fungiform papillae (most)
- Circumvallate papillae (all) (vallate papillae)
- Filiform papillae (none)
Filiform papillae increase friction between the tongue and food to aid propulsion
Tongue
Accessory digestive organ composed of skeletal muscle held together by connective tissue
Gustation (taste) is detected by most papillae found on the tongue
- Foliate papillae (most)
- Fungiform papillae (most)
- Circumvallate papillae (all) (vallate papillae)
- Filiform papillae (none)
Filiform papillae increase friction between the tongue and food to aid propulsion
Salivary glands functions
Functions:
- Chemical breakdown
- Propulsion (aids with)
3 pairs of glands:
- Parotid (Stenson’s duct)
- Submandibular (Wharton’s duct)
- Sublingual (Lesser sublingual ducts)
Salivary glands are composed of ‘racemose glands’ which consist of large lobules, in which there is:
- Mucous alveoli
- Serous alveoli (ptyalin)
functions of the Pharynx
- Muscular tube forming the digestive and respiratory system
- The nasopharynx is occluded when swallowing
- Larger amounts of lymphoid follicles exist in the tonsils (adenoids) to defend against pathogens like bacteria.
Walls of the pharynx:
- Mucous coat
Nasopharynx – ciliated epithelium
oro- & laryngopharynx – stratified epithelium
- Fibrous coat – thickest layer and encapsulates the tonsils
- Muscular coat – contains 3 constrictor muscles: Superior, Middle and InferiorThese muscles contract to swallow
functions of the Oesophagus
There are 3 natural narrowings of the oesophagus:
- At its commencement
- Level of the left main bronchus
- Level it passes through the diaphragm “oesophageal hiatus”
It is approximately 25 cms long
Structure of the oesophageal wall:
- Outer coat of areolar tissue
- Muscular coat of muscle fibres
- Submucous coat of loose areolar tissue
- Inner mucous coat of stratified squamous epithelium
functions of Peristalsis
The contraction and relaxation of muscle layers in the alimentary tract
- It occurs in waves, which push the contents of the tract onwards
- This process is under the influence of sympathetic and parasympathetic nerves
functions and characteristics of the stomach
The stomach is a J-shaped portion of the GIT, located in the left upper quadrant of the abdominal cavity (Waugh and Grant 2014).
Anatomical regions include:
- Cardia
- Fundus
- Body
- Pylorus
- It is a reservoir for food and liquids
- Produces gastric juices (containing HCL, pepsin intrinsic factor and gastric lipase)
Functions:
- Mechanical breakdown – due to the three layers of muscle fibresPeristaltic waves mix food with gastric juice and propel it into the duodenum
- Digestion – Enzymes like pepsin begin to breakdown proteins
- Absorption – absorbs a few fat-soluble substances (aspirin, alcohol, some drugs)
The mucous membrane forms longitudinal folds when the stomach is empty (Rugal folds/Rugae of mucosa)
The three muscular layers allow for multidirectional compressions to ‘churn’ food, resulting in “Chyme”
Mucous Membrane
Lining consists of columnar epithelial cells:
- Cardiac glands: near the cardiac orifice and mainly secrete mucus
- Gastric glands: in the fundus and body which secrete gastric juice
- Pyloric glands: in the pyloric antrum and secrete mainly mucus
- In the gastric pits, the gastric glands (Parietal and chief cells) produce ‘gastric juice’
- There is a limited amount of absorption in the stomach but there is a lot of preparation for it
Liver, gall bladder and Pancreas (Biliary system)
The liver, gallbladder and pancreas connect to the alimentary tract via the common bile duct and enter the duodenumthrough:
The ampulla of Vater (common duct)
The sphincter of Oddi (muscular sphincter)
Out through the opening called the major duodenal papilla
These are accessory digestive organs
The pancreas is about 12-15 cm long with lobulated texture
It consists of a broad head, long body and narrow tail
The liver is the largest gland in the body, weighs around 1.5kg
Divides into four lobes: Large left, large right, caudate and quadrate
The falciform ligament divides the left and right lobes
The gall bladder is a pear-shaped sac that is approximately 10cm long and hangs inferiorly from the liver
Chemical digestion
Pancreas – Islets of Langerhans:
A-Cells release glucagon
B-Cells release insulin
D-Cells release somatostatin
Liver:
Receives two blood supplies
Hepatic artery (Oxygenated)
Hepatic portal vein (absorbed nutrients)
Secretes bile
Gallbladder
Stores bile secreted from the liver
Small intestine
Functions:
Mechanical breakdown – Segmentation and peristalsis
Digestion - digestive enzymes delivered from pancreas and brush border enzymes attached to microvilli membranes complete digestion of all classes of foods
Absorption – Broken down products e.g. carbohydrates, proteins, fats, vitamins, electrolytes, water
It is sub-divided into 3 sections:
Duodenum approximately 25 cm long
4 parts D1, D2, D3 and D4
D2 – site of the Major papilla/Ampulla of Vater/Sphincter of Oddi
Jejunum approximately 2 metres long
Ileum approximately 3 metres long
Ends at the ileo-caecal valve – this valve prevents backflow
Unlike the stomach the folds do not smooth out when distended
Small intestine
Villi are tiny finger-like projections, covered by simple columnar epithelial cells (enterocytes) which is ‘carpeted’ by microvilli.
Along with blood vessels it contains a lymphatic vessel (lacteal) to transport material that cannot cross capillary walls (Waugh and Grant 2014).
At the base of the villi are the entrances to intestinal glands that secrete a watery intestinal juice.
The intestinal glands also contain endocrine cells that secrete intestinal hormones (Martini, Bartholomew and Bledsoe 2007).
Segmentation in the small intestine
Segmentation is rhythmic local constrictions of the small intestine, mixing food with digestive juices and making absorption more efficient by repeatedly moving different parts of food mass over the intestinal wall (Marieb and Hoehn, 2013).
Segmentation in the small intestine
Segmentation is rhythmic local constrictions of the small intestine, mixing food with digestive juices and making absorption more efficient by repeatedly moving different parts of food mass over the intestinal wall (Marieb and Hoehn, 2013).
Large intestine
Approximately 1.5 metres long
The first section: The CaecumIt is a dilated region with a blind end inferiorly connecting tothe appendix
The colon has four mainparts, which have the same structure and functions. They are:
The ascending colon that passes upwards from the caecum to the level of the liver where it curves to the left at hepatic flexure.
The transverse colon that extends across the abdomen to the area of the spleen where it curves inferiorly at the splenic flexure.
The descending colon that passes down the left side of the abdomen.
The sigmoid, which has an S-shaped curve in the pelvic cavity.
Large intestine
Functions:
Digestion – some remaining food residues are digested by gut bacteria (which also produce some vitamin K and some B vitamins)
Absorption – absorbs most remaining water, electrolytes (largely NaCl), vitamins produced by bacteria and some drugs
Propulsion – peristaltic waves propels faeces toward rectum by mass movements
Storage – Faeces accumulates until it is expelled from the body
Defecation – reflex triggered by rectal distension; eliminates faeces from body
Mass peristalsis is a strong wave propelling faeces along the transverse colon into the descendingIt usually occurs at intervals roughly twice an hour or when food enters the stomach
Appendix (Veriform appendix)
Blind ended tube
Approximately 8-10 centimetres
It shares the same wall structure as the large colon but has more lymphoid tissue.
No digestive function
Positions can vary
Clinical context:
Appendicitis is inflammation caused by an obstruction of the lumen
End of the line – Rectum and Anus
The rectum is a slightly dilated portion of the large intestine measuring about 13 cms long
The anal canal is a short passage that opens exteriorly form the body
Usually the rectum is empty, but when a mass movement pushes the contents from the sigmoid into the rectum, the nerve endings in its walls are stimulated by stretching leading to defecation
It is under control of two sphincters:
The internal sphincter consists of smooth muscles and under control of the autonomic nervous system
The external sphincter consists of skeletal muscle and is controlled voluntarily
Gastrointestinal Tract Summary
There are 9 abdominal regions
6 main functions
Ingestion, propulsion,mechanical breakdown, chemical digestion, absorption and defecation
4 layers of the alimentary tract wall
Mucosa, submucosa, muscularis and serosa
There are two groups of organs that form the digestive system
Gastrointestinal tract (Alimentary tract)
Accessory digestive organs
