Case 4 Flashcards
What is the distinction between a benign and malignant tumour?
A benign tumour has relatively innocent characteristics and will appear to remain localised. Whereas a malignant tumour will invade and destroy adjacent structures and is more likely to metastasise and cause death
What is an adenoma?
A tumor of epithelial tissue with glandular origin
What is a papilloma?
A benign epithelial tumor that grows exophytically (outwards beyond surface epithelium) creating a finger/nipple like projection.
What is a polyp?
A polyp is an abnormal growth of tissue projecting from a mucous membrane.
What is the differance between a pedunculated and sessile polyp.
A pedunculated polyp is attached to the surface it grows from by a long narrow stalk, a sessile polyp is not.
What does the term carcinoma refer to?
Any malignant neoplasm of epithelial cell origin derived from any three of the germ layers.
What is a sarcoma?
A cancer that is derived from cells of mesenchymal origin
what is the rough length and width of the large intestine?
1.5M long and 6.5cm in diameter
What is the term for the valve formed by a fold of mucosa that borders the end of the ileum/ start of the cecum?
The ileocecal sphincter
Roughly how long is the cecum?
6cm
In what quadrant is the cecum found?
The lower right quadrant.
What is attached to the lower end of the cecum?
The appendix
The mesoappendix attaches the appendix to what?
The inferior part of the mesentery of the ileum
The appendix is densely populated by what type of cell that helps it act as a source of immune cells.
lyphocytes
How long is the appendix?
7-8cm
What is the colon’s relationship with the peritoneum?
The ascending and descending parts are retroperitoneal
What are the other names for the right and left colic flexures respectively?
The hepatic and splenic felxures
Where does the sigmoid colon begin what is its course?
It begins at the left iliac crest projects medially to the midline then terminates at about S3
How long is the rectum?
roughly 15-20 cm
What is possible because of the transverse rectal folds in the colon?
The passing of flatus while retain feces
How many transverse folds does the rectum have?
3
describe the curvatures of the rectum?
It has three transverse folds and a antero-posterior curve
What is the name for the last 2-3cm of the rectum what muscle does it pass through?
The anal canal, it passes through the levator ani muscle
Describe the arrangement of the mucous membrane of the anal canal
It is arranged in longitudinal folds called anal columns with depressions called anal sinuses between them.
What make hemorrhoidal veins susceptible to distension/pooling?
They lack valves
What are the two distinct portions of the anus?
internal smooth muscle sphincter and external skeletal muscle sphincter
Unlike in other parts of the GI tract the colon has portions of thickened longitudinal muscle. What are there called?
teniae coli
What is the name for the pouches the colon is divided into that give it a “puckered” appearance?
Haustra
Stimulation by parasympathetic nerves arising from where increases secretion in the colon?
The pelvic region
What are the two types of movement that the colon undergoes in order to aid mechanical digestion?
Mixing movements/haustrations and propulsive/mass movements
How long is each typical haustration? when does it reach its peak contractile strength?
Each haustration typically lasts 60 seconds reach its peak contractillity halfway through this time
Haustrations/mixing movements in the colon are mediated by what kind of innervation?
parasympathetic autonomic motor impulses
How often do propulsive/mass movements happen in the colon in a typical day?
1-3 times
What mediates the initiation of mass/propulsive movements in the colon in response to the stomach filling?
the gastrocolic reflex
how does the strength of a propulsive/mass movement vary over time?
mass movements occur in a series upon initiation it becomes more and more forceful over 30 seconds then relaxes over the course of 2-3 minutes the begins again, this pattern continues for 10-30 minutes
What are the four main substances amino acids are broken down into by bacteria in the colon which two are excreted mostly in feces and contribute to its odor?
indole, skatole, hydrogen sulfide and fatty acids. Indole and skatole contribute to odor.
which breakdown product of bilirubin contributes to the color of faeces?
stercobilin
What are the main two vitamins that are both produced by colon bacteria and are required for normal metabolism.
B and K
What are the main roles of the proximal and distal halves of the large intestines respectively?
The proximal half is mostly for absorption whereas the distal half is predominantly for storage.
What ion is actively transported out of the large intestine what two effects does this have?
Na is actively transported creating and electrical chemical gradient which draws Cl out and an osmotic gradient that draws water out.
Faeces is composed of how much water and solid matter proportionally?
75% water 25% solids
What proportion of the solids in faeces is composed of dead bacteria?
30%
What proportion of the solids in faeces is composed of fat?
10-20%
What proportion of the solids in faeces is composed of inorganic matter?
10-20%
What proportion of the solids in faeces is composed of protein
2-3
What proportion of the solids in faeces is composed of undigested roughage, dried constituents of digestive juices and sloughed epithelial cells?
30%
What two compounds are responsible for the color of faeces?
stercobilin and urobilin, derivatives of bilirubin
The external anal sphincter is controlled by what nerve?
pudendal
What are the two defecation reflexes?
The intrinsic and parasympathetic defection reflexes.
What co-ordinates the intrinsic defecation reflex?
the myenteric/auerbach’s plexus.
How is breathing effected by defecation?
a deep breath is taken in before defaction
What happens to the glottis during defecation?
it closes
What happens to the abdominal wall muscles during defecation?
it contracts forcing the contents of the colon downwards
what happens to the pelvic floor during defecation?
It relaxes
What happensto the anal ring during defecation?
it is pulled outward envaginating the feces
What are the two types of carcinogens?
mutagenic and non mutagenic
How can something that is not mutagenic still be a carcinogen?
it can promote cancer through stimulation of mitosis
What is atrophy in cells?
decrease in size
What is hypertrophy
increase in cell size
what is hyperplasia?
abnormal multiplication of cells
What is metaplasia?
transformation of one tissue type to another
What is dysplasia?
loss of normal tissue arrangement/structure
What is the most extreme disturbance of cell growth?
Anaplasia
What is neoplasia?
an abnormal mass of tissue
What is the most common class of cancer?
carcinoma
What type of cell are carcinomas derived from?
epithelial
What type of cell are leukaemias derived from?
blood forming tissues
What are the two main types of sarcomas?
bone and soft tissue
What type of cell are sarcomas derived from
connective tissues
What type of cancer is more common in children?
blastoma
What type of cells are blastomas derived from?
precursor cells
What is a teratoma?
A tumor with tissue or organ components resembling more than one germ layer
What is an oncovirus
a virus that can cause a cancer
In what phase of the cell cycle is DNA replicated?
s phase
How long does S phase usually take?
8 Hours
How long does G2 phase usually take?
2 hours
In what phase of the cell cycle do the chromosomes begin to condense?
G2
In what phase of the cell cycle does mitosis usually occur? How long does this phase usually last?
M phase, it typically lasts an hour
In what phase does cell growth and duplication of organelles occur as well as the normal functions of the cell? How long does this phase last?
G1, it can last from 6 hours to several days or longer
What are the two key classes of regulatory molecules that determine a cell’s progression through the cell cycle?
cyclins and cylcin dependant kinases
What is the difference in the synthesis of CDK’s and cyclins
cyclin dependant kinases are constantly expressed while kinases are only expressed during specific stages of the cells cycle
What is the action of CDK’s once activated?
they phosphorylate specific target proteins, activating or deactivating them
What are the two families of genes that prevent the progression of the cell cycle and act as tumor suppressors.
Cip/kip family and INK4 family
Members of the cip/kip gene family inhibit the effect of what? what is the effect of this?
INK4They inhibit the activity of CDK4 and CDK6 arresting the cell in G1 phase
What are the four members of the INK4 family?
p15 p16 p18 and p19
What part of the cell cycle do the cip/kip family arrest the cell cycle in?
G1
What is hyperchromatism?
the darker staining of cytoplasm and nuclei often observed in cancer cells
Tumor cells are constricted to what thickness if angiogenesis does not occur?
1-2mm in diameter
What is extravasion?
The exiting of cells from the lumen of a vessel to the surrunding tissue
What family of proteases is most important to the process of apoptosis? How are they stored in cells?
caspases are the most important type of protein they are stored in cells as caspases.
Bax and Bak are what?
pro apotitic proteins
Bcl-2 and Bcl-Xl are what?
anti apoptitic proteins
What is a cell’s response to the presence of Bac and Bax into the cell, what is the effect of this?
cytochrome c is released leading to the activation of the caspase cascade.
What is the mos common abnormality in the proto-oncogenes in human tumors
RAS oncogene
What proportion of human tumors contain a mutation of the p53 tumor suppressor gene?
over 50%
What is the main role of the APC
to decrease the amount of growth promoting signals
