Lecture 13: Digestion And Diet Flashcards
What is the evidence of autralopithicines being omnivorous incorporating fibrous or gritty plant foods?
Dentition
What is the evidence for A. Robustus and Africanus having a herbivorous diet with fruit?
Tooth microwear
What is the evidence for the diet of hominins including meat or animal products?
Cut marks, fractures or animal bones and association of stone tools and animal bones
What evidence is provided for the modern human diet including dependence on animal foods and rich, less bulky foods such as meat?
Poor synthesis of taurine and some fatty acids.
Relatively short gut and rapid passage of food
What are the dietary adaptations for fruit eaters?
Broad incisors
Low rounded molar cusps
Long small intestine
What are the dietary adaptations for gum eaters?
Stout incisors
Claws for clinging
Long cecum
What are the dietary adaptations for leaf eaters?
Well-developed molar shearing crests Small incisors Large cecum Complex stomach Enlarged long intestine
What are the dietary adaptations of insect eaters?
Sharp cusps
Short, simple gut
What is Kay’s threshold?
Body weight (~500 g) that separates primarily insectivorous from noninsectivorous primates
What is the peritoneum and what are its layers?
A serous membrane
- Parietal layer: lines the body wall and has abundant pain fibers via nerves form the body wall
- Visceral layer (serosa): covers viscera and lacks pain fibers
What is characteristic of intraperitoneal organs?
- covered on most sides by visceral peritoneum
- Suspended by mesentery from the body wall
What is characteristic of retroperitoneal organs?
- Lie deep to the parietal peritoneum
- covered by parietal peritoneum on one side only
What organs are considered intraperitoneal organs and have a mesentery and are completely covered by the peritoneum?
- Stomach
- Small intestine
- Spleen
- Liver
- Gall bladder
- Cecum with vermiform appendix
- Large intestine
- *The ones listed above are all “abdominal”**
- Uterus
- Ovaries
- Uterine tubes
- *there are all considered pelvic**
What organs are considered extraperitoneal organs which have either no mesentery or lost it during development?
- Kidneys
- Suprarenal glands
- Uterine cervix
- *above are primarily retroperitoneal
- Duodenum
- Pancreas
- Ascending and descending colon
- Rectum
- *above are secondarily retroperitoneal
- Urinary bladder
- Distal ureters
- Prostate
- seminal vesicle
- Uterine cervix
- Vagina
- Rectum
- *above are all infraperitoneal
What supplies blood to the foregut?
Celiac trunk
What does the foregut consist of?
- Esophagus
- Stomach
- Duodenum
- Liver
- Gallbladder
- Spleen
- Pancreas
What supplies blood to the midgut?
Superior mesenteric artery
What makes up the midgut?
- Duodenum
- Jejunum
- Ileum
- Cecum and appendix
- Ascending colon
- 2/3 of transverse colon
What supplies blood to the hindgut?
Inferior mesenteric artery
What makes up the hindgut?
- 1/3 transverse
- Descending and sigmoid colon
- rectum and anal canal
At what level does the thoracic esophagus pierce the diaphragm? What is this called?
T10
The esophageal hiatus
**slightly left of midline
What happens once the thoracic esophagus pierces the diaphragm and where does this occur?
It turns sharply left to enter the stomach at the cardiac orifice
~T11
About how long is the abdominal esophagus?
2.5 cm
What is characteristic of the esophageal sphincter?
It’s physiologic, not well defined anatomically
What are openings in the diaphragm called?
Hiatuses
What structure passes through the diaphragm at T8
Inferior vena cava
What structure passes through the diaphragm at T 12?
Aorta
What is a sliding hiatal hernia?
- Esophageal hiatus of diaphragm enlarges or weakens
- Abdominal esophagus and parts of the stomach (cardia and sometimes fundus) herniate into the thorax
What is a paraesophageal hiatal hernia?
- Defect in diaphragm next to the esophageal hiatus
- Permits fundus of stomach to herniated (not usually the esophagus)
Why do humans typically ingest less food than predict for their body size?
Because we are really good at storing fat and good an taking in food with a very nutrient rich high caloric value
Where is the stomach located? Where is the left end fixed at? Right end?
Left hypochondriac and epigastric regions
- Left end fixed at T10-11
- Right end fixed at L1-2
What are the parts of the stomach?
- Fundus (cranial part of stomach)
- Cardiac part, cardiac orifice (attached to esophagus)
- body
- Pylorus (pyloric antrum is entrance to pylorus)
What is the rugae of the stomach?
Longitudinal folds in the stomach
What is the pylorus/pyloric sphincter/pyloric orifice?
Lowest part of stomach. Pyloric sphincter determines passage of food to duodenum.
Pyloric orifice lines the sphincter and is the entrance to the duodenum
Which curvature (lesser or greater) is found on the side of the stomach closes to the esophagus?
Lesser curvature
Which curvature (lesser or greater) of the stomach is found opposite the esophagus?
greater curvature
What are the 3 parts of the small intestine?
Duodenum
Jejunum
Ileum
How is the duodenum shaped? How long is it?
C-shaped
10 inches long
Where is the duodenum located approximately at? Where does it start and end at?
L1-L4
Starts at pylorus of the stomach and ends at the duodenal-jejunal junction
What are the 4 parts of the duodenum?
- Superior
- Descending
- Horizontal
- Ascending
What “type” of organ is the duodenum considered? What is it covered by?
Secondarily retroperitoneal (except for some of the 1st and 4th parts)
- Covered anteriorly by peritoneum except where the mesocolon of the transverse colon crosses the 2nd part.
- The first part is surrounded by the hepatoduodenal ligament
Where does the root of the mesentery begin at?
The duodeno-jejunal flexure
Where does the superior duodenum start at? How long is it and what holds it in place?
Starts at the pyloric sphincter
~2 inches lone
Held in place by the hepatoduodenal ligament
What is the widened area of the superior duodenum referred to as?
Duodenum bulb
About how long is the descending duodenum and what “type” of organ is this considered?
~3 inches long
All secondarily retroperitoneal
Where do the bile and pancreatic ducts enter into he duodenum?
Second part of duodenum (descending portion) at the major duodenal papilla
Where do the superior mesenteric artery and vein and the root of the mesentery cross the duodenum?
Anterior surface of the 3rd part of the duodenum (horizontal part)
Is the ascending duodenum covered by peritoneum?
No
What holds the ascending duodenum in place?
The suspensory ligament (or muscle) of the duodenum (of Treitz)
Anchors the 4th part of the duodenum to the R crus of the diaphragm
What occupies most of the peritoneal cavity of the abdomen and pelvis?
Jejunum and ileum
About how long are the jejunum and ileum?
~20 ft
Where does the jejunum begin at? Where does the ileum end at?
Jejunum begins at duodenal-jejunal junction and the ileum ends at the ileo-cecal valve
What is characteristic of the jejunum and ileum and what holds these to the posterior wall?
They are very mobile
THE mesentery
How does the large intestine lie in relation to the jejunum and ileum?
It “frames” it
What are the jejunum and ileum often referred to as?
“Free” small intestine
About how long is the jejunum? What part (how many fifths) of the free small intestine is this?
8-10 feet long
2/5ths of the free small intestine
What is characteristic of specifically the jejunum?
- Simple vascular arcades
- Long vasa recta
- More vascular
- Greater diameter
- Thicker
- More plicae circularis
**more blood supply, surface area leading to more nutrient absorption
About how long is the ileum and about how much of the free small intestine does this make up?
10-12 feet long
3/5ths of the free small intestine
What is characteristic of the ileum specifically?
- Compound vascular arcades
- shorter vasa recta
- less vascular
- smaller diameter
- thinner wall
- fewer plicae circularis
Meckel’s diverticula can be a feature of what aspect of the gut? What’s another name for this?
Ileum
Ileal diverticula
What is the most common congenital anomaly of the small intestine? What percent of the population does this occur in?
Meckel’s (ileal) diverticulum
2% of the population
Where would the Meckel’s diverticulum occur at? On average how long is it?
About 2 feet form the i Leo-cecal junction
~2 inches long
What is the meckel’s diverticulum a remnant of?
the vitelline duct
What is the Meckel’s diverticulum clinically difficult to distinguish from?
Appendicitis
About how long is THE mesentery at the root? About how long at its intestinal border?
15 cm (6-7 inches) 20 ft at its intestinal border
What level does the mesentery cross at? Where is this in relation to the duodenum?
LV1-2
3rd part of duodenum
What all does THE mesentery cross?
3rd part of duodenum Aorta IVC R ureter R gonadal vessels R psoas major Ends at R SI joint
What makes up THE mesentery?
2 layers of peritoneum with nerves, lymph nodes and vessels, fat, arteries and veins running between them
What are the regions of the large intestine (8)?
- Cecum and vermiform appendix
- Ascending colon
- Right colic flexure
- Transverse colon
- Left colic flexure
- Descending colon
- Sigmoid colon
- Rectum and anal canal in pelvis
Is the large intestine mobile?
Yes highly mobile and location of its parts is variable
What are the main functions of the large intestine?
Fecal formation, transport and evacuation, water absorption and mucus secretion
What are the taenia coli and what is their function?
3 bands of longitudinal muscle on the outside of the colon. They converge at the root of the appendix. They produce haustrae (sacculations) that slow the movement of feces.
What are the appendices epiploicae?
- Tags of fat
- characteristic of the large intestine
Does the cecum have epiploic appendages?
No
Where is the “blind pouch” of the cecum located?
Inferior to the iliocecal orifice
What is the iliocolic valve?
2 fold that are not a true sphincter of the cecum
What is the ileal papilla?
A cone-like projection of the ileum into the cecum
Where is the opening for the appendix in the gut tract?
In the cecum specifically inferior to the ileal papilla
Where is the vermiform appendix usually attached and located?
Usually attached to the postero-medial part of the cecum
-located at the junction of 3 taenia coli
How long is the vermiform appendix and what is this supported by?
9-10 cm long and supported by a mesoappendix
What is characteristic of the ascending colon?
-Secondarily retroperitoneal except the lowest part
What is characteristic of the transverse colon?
Intraperitoneal (transverse mesocolon)
What is characteristic of the descending colon?
Secondarily retroperitoneal
What is characteristic of sigmoid colon?
Intraperitoneal (sigmoid mesocolon)
What is the function of the spleen?
Acts as a filter for blood as part of the immune system. Old RBCs are recycled in the spleen and platelets and WBCs are stored there. The spleen also helps fight certain kinds of bacteria that cause pneumonia and meningitis
What region of the body is the spleen located in?
Left hypochondriac region
Which ribs does the spleen parallel and where is it located in relation to the stomach?
Parallels left ribs 9, 10, and 11.
Located mid axillary line between stomach and diaphragm
**about the size of a hand
What are the peritoneal relationships of the spleen?
- Covered by peritoneum
- develops in the dorsal mesentery from mesoderm (gastrosplenic ligament and splenorenal ligament)
What are the 3 types of impressions found on the visceral surface of the spleen?
Colic, gastric and renal impressions
The visceral surface of the spleen has a hilum with which 2 ligaments?
Gastrosplenic and splenorenal ligaments
What type of organ is the pancreas?
Secondarily retroperitoneal
Where is the pancreas located?
About L1-L2
What are the 4 parts of the pancreas?
Head
Body
Neck
Tail
What are the 2 main functions of the pancreas?
Exocrine and endocrine
What is the exocrine function of the pancreas?
It is 2 glands that are intimately mixed together into one organ. The bulk of it is composed of exocrine cells that produce enzymes to help with the digestion of food. They release their enzymes into a series of ducts. The main duct runs the length of the pancreas and drains the fluid produced by the exocrine cells into the duodenum.
What is the endocrine function of the pancreas?
Composed of small islands of cells, called islets of Langerhans. These cells dont release their secretions into the pancreatic duct, but they release their hormones into the blood stream.
What does the tail of the pancreas lie against?
The spleen
The main or major pancreatic duct joins the ______ duct and they enter the ______ part of the duodenum together through a common _______________ __________. This forms the major __________ ________.
Bile
2nd
Hepatopancreatic ampulla
Duodenal papilla
Where does the accessory pancreatic duct (if present) enter the duodenum at?
The more superior minor duodenal papilla
Where is most of the liver located in the body?
upper right quadrant
Where is the smaller left lobe of the liver located?
Left upper quadrant
What are the 6 main functions of the liver?
- Regulates composition of the blood
- Removes bilirubin, ammonia, and other toxins from the blood.
- Processes most of the nutrients absorbed by the intestines during digestion and converts those into forms that can be used by the body.
- Produces cholesterol and certain important proteins like albumin
- Produces clotting factors
- Metabolizes alcohol and many drugs
What are the 4 lobes of the liver?
- Left
- Right
- Caudate
- Quadrate
What is the name of the double layer of peritoneum that connects liver to the anterior wall?
Falciform ligament
The peritoneum of the liver splits to enclose a “bare area” of the liver. What does this area include?
The area where the IVC is posterior and the hepatic veins drain into it
What is the porta hepatis?
-A transverse fissure between caudate and quadrate lobes that transmits the portal triad (hepatic artery, portal vein and bile duct)
Where is the ligamentum teres found and what is it?
In the edge of the falciform and is the obliterated umbilical cord
What is the ligamentum venosum?
The “old” ductus venosus
-used to connect the umbical vein with the inferior vena ccava
Where is the gall bladder located?
In the hepatic fossa
What is the fundus of the gall bladder?
- The lowest, widest part
- Contracts anterior abdominal wall at the midclavicular line, 9th or 10th costal cartilage
- usually located on the transpyloric line
What is the main function of the gall bladder?
Reservoir for bile and concentrating bile
What are the 3 parts of the gall bladder?
Fundus
Body
Neck
What are the extrahepatic bile passages?
- R hepatic duct
- L hepatic duct
- together form the common hepatic duct
- Cystic duct
- Bile duct
What collectively forms the bile duct?
Cystic and common hepatic ducts
For an animal with a diet consisting of tough foods (like leaves) they would have a higher measure of which variable when looking at dental wear?
epLsar
For an animal with a more varied diet, the measure of which value would be higher when viewing dental wear?
Asfc (area (scale fractal) complexity)
According to the Alisson-Silvia article, would did they say was not a factor for increased risk of disease/cancer and what was?
-Atherschlerotic and carcinogenic risks are not specific to cooking red meat
- There is an argument for the role of denatured heme in cancer risk
- There is an increased risk for introduction of infectious agents in the meat
- There is an increased risk upon the introduction of non-human sialic acid N-glycoylneuraminic acid into cells
