ANATOMY - Term Test 5 (Digestive System) Flashcards
The organs of the digestive system together perform a vital function, which is:
preparing nutrients for absoprtion and for use by the body
Digestion
The complete process of altering the physical and chemical composition of ingested food material so that it can be absorbed and used by body cells
Main organs of the digestive system form a tube that goes all the way through the _______ cavities of the body, and opens at both ends. This tube is called:
ventral
alimentary canal/digestive tract/gut
Gastrointestional (GI) tract
refers ONLY To the stomach and intestines (somtimes used in reference to entire alimentary canal)
Upper digestive tract structures
Mouth
Pharynx
Esophagus
Stomach
Lower digestive tract structures
- small intestine: duodenum, jejunum, ileum
- large intestine
- cecum
- colon: ascending colon, transverse colon, descending colon, sigmoid colon
- rectum
- Anal canal
Accessory organs of the digestive system (10)
- Salivary glands
- Parotid
- Submandibular
- Sublingual
- Tongue
- Teeth
- Liver
- Gallbladder
- Pancreas
- Vermiform appendix
Provide the length (or range of length) of the following:
Upper digestive tract
Small intestine
Large intestine
Upper digestive tract: 0.5m
Small intestine: 6 - 8 m
Large intestine: 1.5 - 1.8 m
True or False. The digestive tract is outside of the internal environment of the body
True. The digestive tube itself passes through the ventral body cavities but it is really outside the body’s internal environment.
How many layers are in the GI tract?
4 layers
1) mucous lining
2) submucous coat of connective tissue with main blood vessels of the tract embedded in them
3) muscular layer
4) fibroserous layer
Mesentery
Large, fanlike fold of serous membrane (projection of the parietal peritoneum) that connects GI tract to the abdominal wall (connects the parietal and visceral portions)
This is where blood vessels and nerves travel through to reach GI tract; allows free movement of each coil of the intestine and helps prevent strangulation of the long tube
From outside to inside, what are the layers of the GI tract?
serosa, muscularis, submucosa, mucosa
Mucosa
- innermost layer of GI wall (faces the lumen of the tube)
- made of three layers:
- mucous epithelium (inner)
- lamina propria - loose layer of fibrous connective tissue
- muscularis mucosae - thin layer of smooth muscle
Submucosa
- composed of connective tissue that’s thicker than mucosal layer
- contains numerous small glands, blood vessels, and parasympathetic nerves that form the submucosal plexus (Meissner plexus)
Muscularis
- thick layer of muscle tissue that wraps around submucosa
- has an inner layer of circular smooth muscle and an outer layer of longitudinal smooth muscle
- contains nerves organized into a plexus (Myenteric plexus or Auerbach plexus) - lies between the two muscle layers
The Meissner and Auerbach plexuses are collectively called ___________ and comprise the major part of the ________ nervous system.
What important role to these plexuses play?
intramural plexus; enteric nervous system (ENS)
Role: regulation of digestive tract movement and secretion
Serosa
- outermost layer of GI wall
- made up of serous membrane
- actually the visceral layer of the peritoneum (the serous membrane that lines the abdominopelvic cavity and covers its organs)
True or False. The four layers that form the GI tract wall stay consistent in structure throughout the entire tract.
False. It’s the same four layers BUT their structures vary in different regions of the tube throughout its length
How are the esophagus wall layers modified?
- Mucosa layer: stratified squamous epithelium (resists abrasion)
- two muscle layers:
- inner one is circular fibers
- outer is longitudinal fibers
- striated muscle in upper part and smooth muscle in lower part of esophagus and rest of tract
- Serosa: outer layer, fibrous
How are the stomach wall layers modified?
- Mucosa layer: arranged in flexible longitudinal folds (rugae); allow for distension; also has gastric pits with glands
- Muscular layer: has 3 layers instead of just 2
- circular, longitudinal, and oblique fibers
- two sphincters:
- lower esophageal sphincter (LES) - at entrance of stomach
- pyloric sphincter: stomach exit
- Serosa: outer layer is visceral peritoneum, hands in a double fold from the lower edge of the stomach over the intestines (forms an apron-like structure)
- greater omentum (folds) and lesser omentum (connects stomach to liver)
The mouth is also called the
oral cavity/buccal cavity
Structures that form the oral cavity
- lips (surround the orifice of the mouth and form anterior boundary of the oral cavity)
- cheeks (side walls)
- tongue and its muscles (floor)
- hard palate and soft palate (roof)
Lips are covered externally by __________ and internally by __________ that continues into the oral cavity and lines the mouth.
skin; mucous membrane
Define the following terms related to the lips.
1) Philtrum
2) Tubercle
3) Oral Fissure
1) Philtrum: near the midline of the upper lip, markekd by a shallow vertical groove (think where your cupid’s bow is, piltrum is smack dab in the middle of it); ends at the tubercle (junction between skin and mucous membrane)
2) Tubercle: a slight prominence where the skin and mucous membrane meet (think where the plump part of your lips are)
3) oral fissure: the line of contact between the lips when they are closed
Function of the lips
- keeps food in the mouth when chewing
- senses temperature and food textures before it enters the mouth
- involve with speech sounds (syllables)
Cheeks
- form the lateral boundaries of the oral cavity
- continuous with the lips (in front), lined by mucous membrane that is reflected onto the soft palate and alveolar process of each jaw (forming the gums/gingiva)
- has mucus-secreting glands between mucous membrane and buccinator muscles
Walls of the cheeks are formed in large part by which muscle?
buccinator
Hard palate composition
4 bones: two maxillae, two palatines
Soft palate
- forms a partition between mouth and nasopharynx
- made by muscles arranged in an arch shape
- opening of the arch leads from mouth into oropharynx (called fauces)
- midpoint of the posterior border of the arch is the uvula
Tongue
solid mass of skeletal muscle components (intrinsic muscles) covered by a mucous membrane
Components of the tongue
blunt root, tip, and central body
Upper/dorsal surface of the tongue is what colour and covered by what?
moist, pink, and covered by papillae (rough elevations)
papillae has sensory organs (taste buds)
What are the four types of papillae?
all located on the sides or upper surface of tongue
1) circumvallate: 10-14 large mushroom like papillae that run across the tongue in an inverted v-shape; taste buds located on the sides of the papillae
2) fungiform: found on sides and tips of tongue; taste buds located on the sides of these ones
3) foliate: leaflike ridges on te posterior lateral edges of the tongue, also has taste buds
4) filiform: many of these (distributed over anterior 2/3 of tongue); filamentous and threadlike; NO taste buds
Lingual frenulum
fold of mucous membrane in the midline of the undersurface of the tongue
helps anchor the tongue to the floor of the mouth
Ankyloglossia
congenital condition where the lingual frenulum is too short and hinders tongue movement causing the person to be described as “tongue tied” and have faulty speech
Fimbriate fold (plica fimbriata)
fold of mucous membrane that extends towards the apex of the tongue on either side of the lingual frenulum
Why is it beneficial for drugs to be place sublingually (i.e. what anatomical structures allow for this to be beneficial)?
There are many vessels that are extremely superficial and covered only by a very thin layer of mucous (including deep lingual vein). This makes drugs such as ASA or NTG to be quickly absorbed into the circulation rapidly
Changes in size and shape of the tongue caused by intrinsic muscle contraction assists with what functions?
1) mastication - the muscles assist in placing food material between teeth so that you can chew
2) speech formation - syllables
Why does the tongue have extreme maneuverability?
Because the intrinsic muscles that make up the tongue have their muscle fibers oriented in all directions
Contraction of extrinsic tongue muscles (i.e. those that insert into the tongue buy have an origin on some other structure) allow for what functions?
1) Deglutition (swallowing)
2) Speech
The salivary glands are located (inside/outside) the alimentary canal and provide their exocrine secretions through ______________.
outside
via ducts (from glands into lument of GI tract)
What do the serous cells and mucous cells secrete in the salivary glands?
Serous cells produce a watery secretion that has digestive enzymes
Mucous cells produce mucus
What are the three pairs of major salivary glands?
1) parotid
2) submandibular
3) sublingual
How much saliva gets produced daily?
1 L
Name the minor salivary glands, and how much (total %) do they contribute to the total salivary volume?
Minor salivary glands: buccal, lingual, palatine, labial, molar glands
Contribute <5% of total salivary volume but is important for the hygiene and comfort of the mouth tissues + digestive enzyme production
Parotid glands
- largest of the paired salivary glands
- located between skin and underlying masseter muscle in front of and below external ear
- produce a watery (serous) type of saliva containing enzymes (NO MUCUS)
Parotid ducts
- aka Stensen ducts
- ~5cm (2 inch) long
- penetrate the buccinator muscle on each side and open into the mouth through parotid papilla
Inflammation of the parotid glands is known as what, and it is caused by _____________.
called: mump/parotitis
cause: paramyxovirus
Submandibular glands
- aka mixed/compound glands
- contain both serous (enzyme) and mucus producing elements
- located just below mandibular angle
- irregular shape, size of a walnut
*
Wharton ducts
- ducts of the submandibular gland, opens into the mouth on either side of the lingual frenulum
Sublingual glands
- smallest of the main salivary glands
- lie in front of submandibular glands under mucous membrane that’s covering floor of mouth
- each sublingual gland is drained by 8-20 ducts (Rivinus ducts) that open into floor of the mouth
- produce ONLY a mucous type of saliva
The organs of mastication
teeth
The tooth is made up of 4 special types of connective tissues called ___________. They include:
dental tissues
1) Pulp: soft, fibrous connective tissue with blood vessels and nerves at the corner of each tooth
2) Dentin: hard, mineralized connective tissue similar to bone; forms the body of the tooth
3) Cementum: hard, mineralized connective tissue similar to bone; forms a coat around root of the tooth and helps connect to the jawbone
4) Enamel: hard, mineralized connective tissue; harder than bone; forms hard covering of exposed tooth surfaces
What are the three main parts of a typical tooth
crown, neck, and root
Crown
- exposed portion of a tooth
- covered by enamel (the hardest and chemically most stable tissue in the body)
Composition of enamel
- 97% calcified (inorganic) material
- 3% organic material and water
- develops as an interlocking set of rods that forms an incredibly strong coating over the crown
- withstands abrasive process of mastication
- no longer has any living cells by adult hood so cannot remodel/repair self
Root of tooth
- the part of the tooth that fits into the socket of the alveolar process of upper/lower jaw
- root is not rigidly anchored to alveolar proecss by cement, rather is suspended in the docket by periodontal membane (which has periodontal ligaments and collagen fibers)
Which of the 4 tissue layers of the tooth makes up the greatest proprtion of the tooth body?
dentin
Where is the pulp cavity of a tooh located?
covered by dentin, cavity consists of pulp tissue, blood and lymphatic vessels, and sensory nerves
Dentition
type, number, and arrangement of teeth in the jaws
of primary/deciduous teeth (baby teeth)
of permanent teeth
20 deciduous teeth
32 permanent teeth
Eruption of deciduous teeth (at what age)
- first tooth usually erupts ~6 month, and the rest follow at a rate of 1 or more a month until 20 have appeared
- deciduous teeth generally shed between 6 and 13 y. o
Third molars are also known as
wisdom teeth
If an individual does not form wisdom teeth, then the number of adult teeth would be:
28
Teeth in the upper jaw are called ___________.
Teeth in the lower jaw are called ___________.
maxillary teeth
mandibular teeth
Deciduous teeth are identified by either:
name or capital letters (A, B, C, etc.) applied in a clockwise direction
Permanent teeth are identified by:
Arabic numeral (1, 2, 3, etc.) in a clockwise direction
Deglutition
the act of swallowing which moves a rounded mass of food (bolus) from the mouth ro the stomach
Esophagus
- a collapsible, muscular, mucosa-lined tube ~25cm (10 in) long, extends from pharynx to stomach and pierces the diaphragm on the way down from thoracic to abdominal cavity
- lies posterior to the trachea and heart
- a dynamic passageway for food (i.e. food is being pushed to stomach)
- can be separated into:
- cervical part (esophagus in neck)
- thoracic part (in thorax)
- abdominal part (in abdomen)
Which of the following is not true about the esophagus?
a) The esophagus is normally flattened in the resting state
b) stratified columnar epithelium made up the esophageal mucosa to provide a thick abrasion-resistant lining that protects the esophagus from injury
c) the esophagus is made up of smooth and striated muscle
d) all of the above are true
b) is FALSE. It is made up of stratified squamous epithelium that provides the esophagus protection from abrasion
Describe the muscular layers in the esophagus (i.e. striated or smooth).
Upper third: striated circular and longitudinal layers (voluntary)
middle third: mixed (striated and smooth)
lower third: smooth (i.e. involuntary)
Upper esophageal sphincter (UES) - Structure and Function
Structure:
- in the cervical part of the esophagus
- made up of several muscles
- cricopharyngeus muscle plays the primary role
Function: helps prevent air from entering the esophagus during respiration; relaxation of UES allows burping (the sudden escape of air trapped in stomach and esophagus)
Lower esophageal sphincter (LES)
- aka cardiac sphincter/cardinal sphincter
Structure:
- intrinsic part is located at the junction with the stomach; made of circular muscle layers that are thickest (compared to other parts of the esophagus)
- part of the LES also formed by slinglike oblique muscles to strengthen it to contain the stomach contents while stomach is full and churning
- extrinsic part of LES formed by muscles of the diaphragm at the esophageal hiatus (opening near esophagus and stomach junction)
esophageal hiatus
- opening in the diaphragm that allows passage of esophagus into the abdomen
- can become enlarged and stretched, causing bulging of pars of the esophagus and/or stomach upward into diaphragm/chest (leading to hiatal hernia)
Gastroesophageal reflux disease (GERD)
- desribes backward flow of stomach acid up through LES and into lower part of the esophagus
- causes heartburn (painful sensation); severe episodes can cause asthma attacks, chetst pain, bleeding, narrowing of chronic irritation of the esophagus (erosive esophagitis)
- can be aggravated by foods/beverages, smoking, weight (obesity)
- If left untreated, serious pathological (precancerous) changes in esophageal lining may develop (Barrett esophagus)
- Treatment: elimination of underlying cause, drugs to reduce stomach acid (OTC antacids) or acid-blocking medications, or surgery to reduce lumen size/strengthen LES
Which part of the esophagus is most often damaged by exposure to acid and digestive enzymes from the stomach?
In the last 1-1.5cm part of the abdominal part of the esophagus, where stratified squamous epithelium (pale) is replaced by columnar epithelium (brown)
The stomach can distend depending on food volume, and can usually hold up to _____ liters.
1 to 1.5
Location of stomach in the body
- lies in upper part of abdominal cavity under liver and diaphragm
- 5/6ths of its mass left of the median line
- lies in epigastrium and left hypochondrium
- its position can change frequently (pushed down on inspiration, upwards with expiration)
Major divisions of the stomach
fundus, body, and pylorus
Fundus: enlarged portion to the left and above the opening of the esophagus into the stomach
Body: central part of stomach
Pylorus: lower portion of stomach
Cardia/cardiac part of stomach
small margin of the stomach at the junction between esophagus and stomach
Stomach: Lesser curvature vs greater curvature
Lesser curvature: curve formed by upper right surface of stomach
Greater curvature: curve formed by lower left surface
cardiac sphincter vs. pyloric sphincter
Cardiac sphincter: controls the opening of the esophagus into the stomach
Pyloric sphincter: controls the opening from the pyloric portion of the stomach into first part of the small intestine (duodenum)
Epithelial lining of the stomach is thrown in folds called _____ and marked by depressions called _______.
rugae; gastric pits
The three major secretory cells in the gastric glands of the stomach are:
chief cells
parietal cells
endocrine cells
Chief cells (zymogenic cells) secrete:
enzymes of gastric juice
Parietal cells secrete
HCl (and are also thought to produce instrinsic factor, which binds to B12 to protect them from digestive juices until they reach small intestine to facilitate B12 absorption)
Endrocrine cells secrete
ghrelin (GHRL) - hormone that stimulates hypothalamus to secrete GH and increase appetite
gastrin - which influences digestive functions
The muscularis (muscle layer) of the stomach is arranged how? How does this provide benefit to its function?
- made of three distinct layers:
- usual layer of longitudinal muscles and circular muscles
- AND additional underlying oblique layer
- crisscrossing pattern of smooth muscle fibers formed gives the stomach wall the ability to contract strongly at many angles (making the mixing action very efficient)
Functions of the stomach (7)
- Food reservoir: main function; stored in stomach til it can be partially digested and moved farther along GI tract
- Secretes gastric juice: has enzymes to aid in digestion
- Churning food: contractions of muscular coat helps to break up food into small particles and mix them well with gastric juice (and then moved along into duodenum)
- Secretes intrinsic factor
- Small amount of absorption: absorbed substances (certain drugs, water, alcohol, short chain FA in butter/milk fat)
- Produces gatrin and ghrelin (GHRL): gastrin - helps regulate digestive functions; ghrelin - increases appetite
- Protection via destruction of pathogenic bacteria in food/mucus from resp tract
Inadequate saliva production causes what?
1) inhibits proper mixing and mastication of food
2) decreases production of salivary amylase (ptyalin) that initiates digestion in the mouth
3) causes an imbalance in salivary pH (7.4)
Sjögren syndrome
- autoimmune disease where immune system targets the salivary and tear glands for destruction
- results in ++reduction in saliva production ⇒ dry mouth (xerostomia)
- makes chewing and swallowing difficult & contributes to a higher incidence of tooth decay
- and ++reduction in tear production ⇒ dry eyes (xerophthalmia)
- causes feelings of irritation and grittiness and progressively worsen
- affects more women, usually begins around 50 y.o.
- Treatment: drugs to stimulate saliva production, use of artifical tears and saliva
Mumps
- acute viral disease characterized by swelling and parotitis (inflammation of the parotid gland) - both glands are involved in ~70% of ppl with mumps
- caused by paramyxovirus
- Sx: fever, loss of appetite, generalized feeling of weakness and discomfort
- Sx progress into swelling of parotid glands, spasm of jaw muscles leading to pain when mouth is opened or during chewing movements
- swelling continues and leads to puffy face
- redness of parotid papillae on inside of cheek opposite second molar tooth on one or both sides of the upper jaw
- often in children (5-15) but can happen in adults
- can also affect joints, pancreas, myocardium, and kidneys (and testes in 25% of males, orchitis, which may lead to some reduction in fertility)
Tooth decay/dental caries
- common disease of the enamel, dentin, and cementum of teeth that results in the formation of a cavity
- decay: demineralization of hard tissues of the tooth caused by acids produced by Streptococcus mutans bacteria (bacteria survives on sugars from food that collects around teeth, forming plaque which is an acid-producing biofilm)
- if untreated, results in infection, loss of teeth, soft tissue inflammation of the mouth
Gingivitis
- inflammation/infection of the gums
- most cases due to poor oral hygiene (inadequate brushing and no flossing)
- may also be a complication of other conditions (DM, vitamin deficiency, pregnancy)
Peridontitis
- inflammation of the periodontal membrane/ligament - anchors the tooth to the bone of the jaw
- leading cause of tooth loss in adults
- often a complication of advanced or untreated gingivitis and may spread to the surrounding bony tissue
- destruction of membrane/bone reuslts in loosening and eventually teeth loss
Leukoplakia of the mouth
- precancerous change in mucous membrane characterized by thickened, white, and slightly raised patches of tissue
- often develops in the fold between cheek and gum in users with smokeless tobacco (the condition called snuff dipper’s pouch)
- can lead to tooth and gum disease + oral cancer
Malocclusion (of the teeth)
- occurs when missing teeth create wide spaces in dentition, when teeth overlap, or when malposition of one or more teeth prevents correct alignment of the maxillary and mandibular dental arches
- overbite: malocclusion resulting in protrusion of upper front teeth hanging over lower front teeth
- underbite: lower front teeth outside upper front teeth
- can cause chronic pain, problems to temporomandibular joint, headaches, difficulties with mastication
- Tx: braces and dental appliances
Cleft lip/cleft palate
- most common congenital defects of the mouth
- caused by failure of structures in the upper lip/palate to duse or close properly during embryonic development
- repaired with surgery: cleft lip repaired soon after birth; cleft palate repair at 1-2y.o.
Many stomach disorders present with what common symptoms?
1) gastroenteritis (stomach and intestinal inflammation)
2) Anorexia - chronic loss of appetite
3) Nausea - unpleasant feeling that often leads to vomiting
4) emesis - vomiting
Ulcer
- craterlike wound or sore in membrane caused by tissue destruction
- cause disintegration, loss, and death of tissue as they erode layers of teh walls of the stomach or duodenum
- cause gnawing or burning pain
- may ultimately result in hemorrhage, perforation, widespread inflammation, scarring, etc.
- primary cause: H. pylori
- Treatment: antibiotics
- Other causes: long term use of NSAIDs (ASA, ibuprofen) - interferes with prostaglandins that regular mucus lining of GI tract
- Treatment: stopping NSAID use
Stomach cancer - Causes and Signs/Symptoms, Treatment
Causes: H. pylori infection, excessive alcohol consumption, chewing tobacco, eating smoked or heavily preserved food
S/Symptoms:
- Early warning signs: heartburn, belching, nausea
- later warning signs: chronic indigestion, vomiting, anorexia, stomach pain, blood in feces
Treatment: removal of tumors
Pylorospasm
common condition in infants where pyloric fibers do not relax normally to allow food to leave the stomach, resulting in infants vomiting their food instead of digesting and absorbing it
Treatment: muscle relaxer
Small intestine measures
2.5cm in diameter, 6-8 meters (20-26 feet) in length
Divisions of the small intestine
duodenum, jejunum, ileum
Duodenum: uppermost division and part where pyloric end of the stomach attaches; ~25cm (10 in) long, shaped like a C
Jejunum: starts where tube turns abruptly forward and downward (after duodenum); 2.5m (8 feet)
Ileum: comes afer jejunum, no sharp demarcation between the two divisions; ~3.5m (12ft) long
The small intestinal lining has circular folds called ______ that have many tiny projections known as ________.
plicae; villi
Each villus contains:
an arteriole, venule, and lymph vessel
villi and microvilli increase SA making it ideal for the main site of digestion and absorption
Enterocytes
absorptive epithelial cells on the surface of villi, looks like a fine brush (collectively called a brush border)
brush border has digestive enzymes
Enteroendocrine cells
also found in villi; produce intestinal hormones
Tuft cells (brush cells)
found on villus in small intestine, have microvilli; secrete prostglandins and endorphins & “taste” intestinal contents to detect the presence of AA and other types of nutrients
Depressions between villi are known as ____________. What is the function of this structure?
intestinal crypts (of Liberkühn) or intestinal glands
serve as a stie for rapid mitotic cell division
Paneth cells
found at the base of intestinal crypts in small intestine
produces enzymes and other molecules to inhibit bacterial growth in the small intestine (protective function)
Length/Diameter of large intestine
Length: 1.5-1.8m (5 or 6 ft)
Diameter: ~6cm (2.5 inch) - decreases toward the lower end of tube
Divisions of the large intestine
cecum, colon, rectum
Cecum: first 5-8cm of large intestine; a blind pouch located in the lower right quadrant of abdomen
Colon: divided into ascending, transverse, descending, and sigmoid colon
Rectum: last 17-20cm of intestinal tube; contains crescent-shaped transverse rectal folds (rectal valves) to slow down flow of feces as it enters rectum and to hold it in place til defecation occurs
Ascending Colon
- lies vertically on R side of abdomen and extends up to lower border of liver
- ileum joins large intestine at junction of cecum and ascending colon (T shape attachment)
- ileocecal valve permits material to pass from ileum into large intestine but not usually in reverse direction
Transverse colon
- passes horizontally across the abdomen, below liver stomach and spleen
- extends from hepatic flexure to splenic flexure (the two points where the colon bends on itself to form 90 deg angles)
Descending colon
- lies vertically on the left side of abdomen, extends from point below the stomach and spleen to level of iliac crest
Sigmoid colon
- portion of the large intestine that heads downward below iliac crest, in S-shape curve
- eventually joins the rectum bending towards the left
Why are patients placed on the left side when being given an enema?
because of the anatomical structure of the sigmoid colon and rectum; in this position, gravity aids the flow of enema fluid from rectum into sigmoid flexure
The terminal inch of the rectum is called the
anal canal
Anal Canal - Structure and Function
- mucous lining arrange in numerous vertical folds (called anal columns) which each contain an artery and a vein
- opening to the exterior is guarded by two sphincter muscles (internal smooth muscle & external striated muscle)
- opening itself is called anus
The anus is directed slightly _________ and therefore at almost _________ to the rectum
posteriorly; right angle
GI wall is modified to have intestinal mucous glands. What is the function of this?
these mucous glands produce lubricating mucus that coats the feces as they are formed
True or False. Large intestine contain villi and microvilli.
False. Large intestine do have microvilli, but the cells that make up the large intestine do not form villi like those in the small intestine.
Describe the modified muscular layer changes in the large intestine.
- colon has an uneven distribution of fibers in the muscle layer
- longitudinal muscles are groups into tapelike strips (~1cm wide) called teniae coli
- circular muscles grouped into dense rings - allows for the formation of pouchlike haustra (look like puckered segments of colon; promotes segmentation in the colon)
- outside of the colon wall is the serous membrane extension of the peritoneum (often studded with pouchlike extensions filled with fat called epiploic appendages)
Vermiform appendix
- wormlike tubular organ (8-10 cm), most often found just behind cecum or over pelvic rim
- lumen of the appendix communicates with cecum 3cm below the ileocecal valve
- has lymph nodes on its wall shortly after birth, get more prominent up til first 10 years of life and then progressively disappear
- Function: unknown, known as a vestigial organ
- serves as a breeding ground for nonpathogenic intestinal bacteria found throughout the colon (which contribuets to digestive process, production of essential molecules, and flatulence)
Appendicitis
- inflammation of the appendix
- can be due to food, fecal matter, appendicoliths (stone-like concretions) that become trapped in opening and block the lumen, causing irritation and inflammation
- Dx: McBurney point (a site on the surface of the anterior abdominal wall)
- located in RL quadrant of abdomen, about 1/3 of the way along a line from right anterior superior iliac spine to the umbilicus
- will have extreme sensitivity and pain on palpation
- opening between appendix and cecum is often completely obliterated in elderly, so low incidence of appencitis in elderly
Peritoneum
large continuous sheet of serous membrane that lines the walls of the entire abdominal cavity (parietal layer) and forms the serous outer coat of the organs (visceral layer)
intraperitoneal vs extraperitoneal
Intraperitoneal: within the peritoneum; organs that are considered intraperitoneal would be covered with visceral peritoneum
Extraperitoneal: outside the peritoneum
The extraperitoneal space along the posterior and bottom of the abdominopelvic cavity is called _______________
retroperitoneal
Retroperitoneal organs
pancreas (except the tail), kidneys and adrenal glands, ureters and bladder, aorta and inferior VC, part of esophagus, part of duodenum, ascending and descending colon, rectum
Transverse Mesocolon
similar to mesentery but a less extensive fold of peritoneum; attaches the transverse colon to the posterior abdominal wall
Greater omentum
- continuation of the serosa of the greater curvature of the stomach and the first part of the duodenum to the transverse colon
- where deposits of fat accumulate
- looks like a lace apron hanging loosely down over the intestines
- in cases of abdominal inflammation, the greater omentum envelops the inflamed area to wall it off from the rest of the abdomen
Lesser Omentum
- attaches from the liver to the lesser curvature of the stomach and the first part of the duodenum
True or false. The liver is the largest gland in the body.
True. weighs about 3-4lbs (1.5kg)
True or False. The liver grows and shrinks by nearly 40% daily affected by our eating schedule
True
Lobes of the liver
- two lobes separated by falciform ligament
- L lobe: forms 1/6th of the liver
- R lobe: makes up the remainder and has three parts
- R lobe proper
- Caudate lobe (small oblong area on posterior surface)
- Quadrate lobe (4-sided section on undersurface)
- each lobe divided into numerous lobules by blood vessels and fibrous strands that form a support framework (perivascular fibrous capsule/capsule of Glisson) and this capsule is an extension of of the connective tissue capsule that covers the entire liver
Location of the liver
lies immediately under the diaphragm, attached to peritoneal extensions (coronary ligaments)
occupies most of the R hypochondrium and part of epigastrium
______________ are anatomical units of the liver, which are shaped like tiny hexagonal or pentagonal cylinders. These structures contain liver cells which are known as ___________.
Hepatic lobules; hepatocytes
Portal triad/hepatic triad
a set of tiny tubes that run along the outer corners of each hepatic lobule, contains:
- interlobular artery (branch of the hepatic artery)
- interlobular portal vein (branch of the portal vein)
- interlobular bile duct
each portal triad also has lymphatic vessels and branches of the vagus nerve
What main macrophage lines in the sinusoids of each liver lobule? What is their function?
Stellate macrophages (Kupffer cells) - found along the lining of the sinusoids
Function: to remove bacteria, worn RBCs, and other particles from the bloodstream
Bile is formed by
hepatocytes
Describe the pathway of blood through the liver.
- blood enters lobule from branches of hepatic artery and portal vein
- arterial blood oxygenates hepatocytes (whereas blood from portal system just passes through liver for inspection)
- phagocytes remove stuff from the bloodstream that is no longer needed
- blood continues along sinusoids to central (intralobular) vein
- central vein leads to main hepatic veins that drain into IVC
Describe how small bile ducts join to become the common bile duct.
Small bile ducts ⇒ join to form two larger ducts (R and L hepatic ducts) ⇒ join to form common hepatic duct ⇒ merges with cystic duct to form ⇒ common bile duct
The small “collecting” area for bile and pancreatice juice is called ____________ and is made up of what two ducts?
hepatopancreatic ampulla (which then empties into duodenum at the major duodenal papilla)
made of: common bile duct merged with pancreatic
Main functions of the liver (8)
- Detoxify various substances
- Liver cells break down/remove old RBCs recycling iron from Hb
- regulate brain’s appetite centers
- Liver cells secrete ~0.5L (~1 pint) of bile daily
- Liver cells carry out multiple components of metabolism of proteins, fats, and carbs
- Liver cells store several substances (iron, vitamins A, B12, and D)
- produces plasma proteins including clotting factors and albumin
- Liver serves as a site of hematopoiesis (blood cell production) during fetal development
What happens to toxic substances after detoxification by liver cells?
They are changed into non-toxic compounds through a series of chemical reactions
Main components of bile
bile salts, bile pigments and cholesterol
Bile salts
- formed in the liver from cholesterol
- the most essential part of bile
- aid in digestion and absoprtion of fats and then are themselves absorbed in the ileum; also serves as pathway for elimination of certain RBC breakdown products (bilirubin)
- 80% of bile sats recycled in the liver to be part of bile again
Gallbladder - Location and Appearance
Location: lies on the undersurface of the liver and is attached there by areolar connective tissue
Appearance: pear-shaped sac 7-10cm long (3cm broad at its widest)
Gallbladder - Structure and Function
Structure: wall made of serous, muscular, mucous layers; mucosal lining arranged in folds called rugae (similar to stomach)
- reguae allows for gallbladder to expand as it receives bile that backs up into it when sphincters of major duodenal papilla contract
- can hold 30-50ml of bile
Function:
- stores backed up bile (and concentrates it 5 to 10 fold as it’s stored)
- ejects bile into duodenum when partially digested material exits the stomach
Jaundice
yellow discolouration of skin and mucosa due to obstruction of bile flow into duodenum and therefore cannot exist via feces as per usual (instead it’s absorbed into the blood with an excess of yellow hue bile pigments and deposites into tissues)
Cholecystitis
inflammation of the gallbladder; often caused by gallstone formation (cholellithiasis)
may require surgical removel (cholecystectomy) or stone elimination with drugs or nonsurgical methods
Pancreas - Size/Appearance and Location
Size/appearance: grayish, pink coloured gland ~12-15cm long, weighing ~60g
- looks like a fish with head and neck in C-shaped curve
- body extends horizontally behind stomach, tail touching the spleen
Structure of pancreas
- composed of two types of glandular tissue (one exocrine, one endocrine)
- exocrine tissue has cells arranged in grap-like cluster where they release their secretions into a microscope duct that eventually join to become larger ducts and finally into pancreatic duct
Cluster of endocrine cells found in between the exocrine units in the pancreas as known as ___________. These structures contain what kinds of cells?
pancreatic islets
mainly alpha cells and beta cells
Pancreas is described as a dual gland. What does this mean?
It’s an exocrine (duct) gland because of the acinar units (grapelike clusters that release their secrestions into a duct within each unit that eventually join to create pancreatic duct which joins common bilt duct to empty into duodenum)
It’s also an endocrine (ductless) gland because of the pancreatic islets where alpha and beta cells are secreting into blood capillaries and not ducts
Functions of the pancreas
- Digestion: Acinar units (exocrine) secrete pancreatic juice - water and sodium bicarbonate (NaHCO3) and digestive enzymes
-
Metabolism:
- beta cells secrete insulin - controlling carb metabolism
- alpha cells secrete glucagon - opposite effect on carb metabolism
Intestinal diseases often involve what two signs and symptoms
Diarrhea - elimination of liquid feces, perhaps accompanied by abdominal cramps
Constipation - decreased motility of colon, resulting in difficulty in defecation
Malabsorption syndrome
general term referring to a group of symptoms resulting from failure of the small intestine to absorb nutrients properly
Sx: anorexia, abdo bloating, cramps, anemia, and fatigue
Diverticulosis
- presence of abnormal saclike outpuchings of intestinal wall (diverticula)
- often develop in adults >50 who eat low fiber foods and usually asymptomatic
- can become inflamed and turn into diverticulitis
Diverticulitis
Inflammation of the diverticula (saclike outpouchings of the intestinal wall)
characterized by pain, tenderness, and fever
Colitis
- any inflammatory condition of the large intestine
- Sx: abdo cramps or constipation, or abdo cramps; potential bleeding and intestinal ulcerts
- can result from autoimmune disease (such as ulcerative colitis)
- another type: Crohn disease (results from abnormal inflammatory response)
IBS - Irritable Bowel Syndrome
- aka spatic colon
- common chronic noninflammatory condition that is often caused by stress
- characterized by diarrhea or constipation with or without pain
Colorectal cancer
- a malignancy (usually adrenocarcinoma) or the colon/rectum
- often after 50 y.o., risk factors: low fiber, high fat diet and genetic predisposition
- Early warning signs: changes in bowel habits, fecal blood, rectal bleeding, abdominal pain, unexplained anemia or weight loss, and fatigue
Hemorrhoids
- dilated veins that result from direct irritation or from increases in venous pressure that often accompany pregnancy or result from constipation and subsequent straining required to pass hardened stools
- most commonly develop near anal opening or on wall of anal canal
- painful and irrtaing but respond well to treatment
Proctitis
- inflammation of the rectal mucosa
- common cause of rectal bleeding, mucus discharge, increased frequency of bowel movements
- may result from a direct irritation or infection
- Tx: anti-inflammatory drugs and treating underlying cause
Anal fissures
- minor lacerations in the lining of the anus or anal canal that result in rectal bleeding
- caused by direct irritation (often passing hard stool)
*
Anal Fistula
- passageway that often develops between rectal wall and skin surrounding the anus
- often occurs in Crohn disease
Hepatitis
- general term referring to inflammation of the liver
- characterized by jaundice, liver enlargement, anorexia, abdominal discomfort, gray-white feces, and dark urine
- Causes: alcohol, drugs, toxins, bacterial/viral/parasitic infection (i.e. hepatitis A)
Hepatitis C virus (HCV)
- virus that causes hep C and can be transmitted by contaminated blood
- can be chronic and result in life-threatening liver disease months/years after exposure
Cirrhosis
degenerative liver condition (liver failure basically) - liver has been pushed to its limits and its ability to regenerate damaged tissue is not working any longer
Pancreatitis
inflammation of the pancreas
Acute pancreatitis
usually results from blockage of the pancreatic duct, causing pancreatic enzymes to back up into the pancreas and digest it
How can cystic fibrosis (CF) block flow of pancreatic enzymes?
- the condition causes disruptions in cell transport leading to exocrine glands producing excessively thick secretions
- Thick pancreatic secretions may build up and block pancreatic ducts which disrupt flow of pancreatic enzymes and damage pancreas
