MAJOR GLANDS ASSOCIATED WITH ALIMENTARY CANAL .
It is an exocrine gland associated in the buccal cavity. Major salivary glands are :
Parotid gland : largest salivary gland located between skin of cheeks and masseter muscle.
Its duct is called stenson’s duct that innervates the buccinator muscle above the second molar.
Its secretion is purely serous of about 20% of saliva.
Myxo virus affect this gland mainly in babies to cause Mumps .
Sub -mandibular gland : second largest salivary gland ; located just below mandibular angle .
Its duct is called Wharton's duct opening behind lingual frenulum.
Mixed salivary glands producing equal serous as that of mucous secretion; which is the most; 70% of the total saliva,
Sub lingual gland:
Located on the floor of the buccal cavity.
Duct of rivinus is called for it’s duct .
Mucous secretion ; of about 5% ;the least of 3.
Other minor salivary glands contribute rest shares in saliva formation. They are vital to moist your mouth in an idle state of buccal cavity; no food in the cavity.
Seromucinous liquid of Ph 6.2 acidic in idle state.
Consists 99.5% water, the rest are enzymes like ptyalin ( lingual amylase), lipase, electrolytes like Na,cl ions and many others and immunoglobulin A.
1600 ml of it is secreted per day
FUNCTIONS : lubrication and digestion of food,lysogenic role,dissolving solid foods for taste buds reception and immunity too.
Largest visceral organ but second largest organ after skin in case of humans.
Weighs about 1.5 kg in a healthy adult.
Location : below diaphragm in abdominal pelvic cavity.
Divided unequally into right and left lobe divided by falciform ligament, anatomically. Left is smaller ; one sixth the total while the right lobe is the remaining ones. But looking dorsally we can further divide right one to 3 sub parts called right proper, caudate, quadrate. So humans have 4 lobes functionally while frogs have 3 lobes and rabbits have 5.
Intraperitoneal organ but truly covered by fibrous connective tissue called Glisson’s capsule .
27% of CARDIAC OUTPUT reach this organ which is the most of all.
Histology of liver :
Functional unit of the liver is hepatic lobules.
Each lobule is hexagonal with a centrally located vein. Lines of polyhedral cells in intra locular space are called hepatic cord.
In each hepatic cord spaces are called canaliculi while spaces in between 2 hepatic cords are called hepatic sinusoids.
Each vertex of lobules are with a portal triad whose transverse view is with hole of portal vein, artery and bile duct.
80% of total supply are of hepatic portal vein and rest of hepatic arteries.
Cells in lobules can be ito/stellate cells ; which stores fat or kupffer cells ; which are phagocytic or normal bile secreting or storage or producing cells .
Functions of liver :
Main role is production of bile juice secretion.
Short note to bile juice :
An alkaline fluid that is bitter in taste and golden yellow colour .
500 ml per day .
Composition : 86% water and rest 14% includes bile salts of glycolic and taurocholic acids, bile pigment like bilirubin and biliverdin, cholesterol , lecithin , inorganic salts of chlorides and essential component ; carbonates making fluid alkaline.
Bile salts here;
emulsifies fat ; which is breaking large globules to smaller ones which is mechanical digestion.
Neutralizes acidic chyme .
Increases peristaltic movement .
Absorption of fat soluble vitamins.
Bile acids coat the emulsified fats.
Metabolic function :
Glycogenesis : conversion of excess glucose to glucagon in presence of insulin.
Glycogenolysis : reverse of glycogenesis in presence of glucagon.
Gluconeogenesis : formation of glucose from non-carbohydrates source
Lipogenesis : excess protein and fats convert to lipids .
Deamination of acid ; excess of protein gains a lot of ammonia which is converted to urea.
Detoxification of toxins .
Thermogenesis : thermal homeostasis condition in the body.
Synthesis of RBC in babies, blood proteins, heparin, glycogen, fat soluble vitamins. Vitamin B12,angiotensinogen, iron, copper, vitamin A from beta carotenes.
Destruction of RBC and converted it’s protoporphyrin portion to bilirubin and biliverdin.
Immunological role by kupffer ‘s cells.
All the hepatic ductules from each side meet to form the right and left hepatic duct. The sides from both join to form a common hepatic duct which further join with bile duct from gallbladder to form common bile duct . This again joins with a pancreatic duct called duct of wirsung and forms a swollen common hepatic pancreatic ampulla called “ ampulla of vater”.
Sphincter of boyden lies guarding on junction joining with duct of wirsung
While a sphincter of oddi guards the end of ampulla of vater.
Another supplementary duct called the duct of santorini arises from pancreas only, opening right of opening of common hepatic pancreatic ampulla.
Soft , lobulated and retroperitoneal , endodermal and pale greyish pink in colour.
2nd largest gland about 12 -15 cm in length and 60 gm in weight.
Located : behind and below stomach in concavity of duodenum so called, romance of duodenum.
It can be divided into 4 parts :
Bulky head : it is positioned on a curve and exocrine in nature. It posses extra growth off called uncinate portion.
Neck : this is also exocrine part
Body : also exocrine
Tail : this is the endocrine part secreting hormones. This part is in fact intraperitoneal .
Lumen are connective tissues and pancreatic lobules .
Each pancreatic lobule is with many columnar granulated cells .
Their secretions are thrown off the lumen and are connected with the pancreatic duct.
Types of enzymes secreted by those acinar cells : pancreatic amylase, trypsinogen, pancreatic lipase .
Duct cells are responsible to produce bicarbonates under action of secretin hormones.
Lumen of mostly tails, possess endocrine cells called islets of langerhans. This consists of four types of cells :
∝ cells : secretes glucagon
ᵝ cells : secretes insulin .
ઠ cells : inhibits abovementioned cells .
Pancreatic juice :
Alkaline of Ph 8 includes enzymes like pancreatic amylase, trypsinogen, pancreatic lipase and bicarbonates ,sodium, calcium, magnesium, potassium ions .
1500 ml per day secretion.
Functions of pancreas:
Secretes enzymes for digestion.
Hormones for glucose humoral control.
Neutralize acidic chyme .
Histology of alimentary canal :
Tissues from oesophagus to anal canal more or less are similar posssesing 4 layers :
Serosa : this is the outermost layer made up of squamous epithelium . However , this layer is made up of elastic fibrous connective tissue in the oesophagus called tunica adventitia. Because they lie out of coelom .
Muscularis externa : in general there is outer longitudinal muscle and inner circular muscle. But in the stomach there is an extra middle oblique layer. Here there is myenteric/Auerbach’s plexus to create peristaltic waves .
Sub mucosa : this layer possesses connective tissues like areolar ,lymphatic vessels and blood vessels. In the small intestine’s ileum there are wandering cells called peyer’s patch .Meissner's plexus is here to control secretion of glands here. sub mucosa and mucosa both extend inward , fold to form plica circularis/valve of kerckring (but not a valve) . While only mucosa fold to form villi; to fullfill the purpose of effective and more absorption of digested food.
Muscularis interna : outer longitudinal and inner circular muscles like muscularis externa .
Lamina propria: this is a layer of connective tissues and the speciality in duodenal histology is presence of brunner’s gland.
Mucosal epithelium : buccal cavity,oesophagus and anus have stratified squamous epithelium and rest are with simple columnar epithelium.
Gross look to retroperitoneal part of the system :
Pancreas except tail.
Duodenum except 1st part that excludes ampulla of vater . the intraperitoneal region is also a common site for peptic ulcer.
Diagram of histology discussed below :
fig : common histology.