Large Intestine (generic) Principal functions: 1.Recovery of HOH and salts from feces 2.Propulsion of feces into rectum Also divided into three parts. Its total length is approx. 1.5 m long but it has a greater diameter than the small intestine. No villi Intestinal glands – mucus –Crypts of Lieberkühn Surface epithelia – mostly goblet cells and absorptive cells Specialized muscularis externa –Longitudinal muscle is separated into three independent bands
Anatomical Divisions of L. Intestine 1.Caecum: –It is the blind end of the large intestine. Attached to it is the appendix. It is thought to play a role in fighting infection. 2.Colon: –Undigested food enters the colon and water and minerals are absorbed –Intestinal bacteria help break down some of the undigested food so it can be absorbed. –These bacteria also produce vitamin B12 and K as well as some amino acids 3.Rectum and Anal Canal: –Waste material (feces) moves into this region and is expelled through the anus.
Long section of the colon (4x)
Long section of colon (100x) 2 main cell types: 1. goblet cells 2. absorptive cells
Sulculation caused by taeniae coli down to the anus – then continuous sheet of longitudinal muscle.
“End”notes Rectum – end of large intestine –Continuous sheet of long muscle Anus – switches back to strat squam. Goblet cells increase on way down.
SectionEpitheliumCell types in E.Other features EsophagusStratified squamousSquamousSubmucosal glands Gradation of muscle Body / fundusGlandular – straight tubular Surface mucous cells Neck mucous cells Parietal cells Chief (peptic) cells Lymphoid sparse no aggregates PylorusGlandular – coiled, branched tubular Mucous cells Occasional parietal Lymphoid sparse no aggregates DuodenumGlandular with villi and crypts of Lieberkühn Enterocytes with microvilli Goblet Cells Paneth Cells Brunner’s Glands Jejunum / ileumGlandular with villi and crypts of Lieberkühn Enterocytes with microvilli Goblet Cells Paneth Cells Peyer’s patches Colon / rectumGlandular – straightGoblet cells Absorptive cells Teniae coli AppendixGlandular – straight cryptsGoblet cells Tall columnar cells Prominent lymphoid aggregates AnusGlandular – straight Stratified squamous Absorptive and goblet Squamous cells Colums of Morgagni
Pancreas and Liver Developmentally –Glandular outgrowth of primitive gut
Few notes on the Pancreas In curve of duodenum Lobulated Gland separated by septa Exocrine Component – digestive enzymes from acini –can’t secrete active form –digest the gut –secretes proenzyme form (inactive enzyme) Enterokinase (duodenal secretion) – activates proenzyme Endocrine Component – Hormones – sugar metabolism –Insulin and Glucagon – decrease and increase blood sugar levels Islets of Langerhanz –secreted into bloodstream –lots of capillaries associated with islets
1.Central lumen 2.Intercalated duct 3.Intralobular ducts 4.Interlobular ducts 5.Pancreatic duct 6.Ampulla of Vater 7.Duodenum
Exocrine Acinus (8500x)
Liver Major functions –Detoxification of metabolic waste (deamination of amino acids – urea), drugs, toxins, alcohols –Destruction of spent RBCs and reclamation of their constituents (spleen does this too) –Synthesis and secretion of bile (consists of above) –Synthesis of lipoproteins, plasma proteins (including albumin and clotting factors) –Synthesis and storage of glycogen
Liver Largest gland in body (1500g) Divided into 4 lobes (R, L, quadrate and caudate) Endocrine and Exocrine components –Both are roles of the hepatocytes (liver cells) –Exocrine – bile –Endocrine – lots of stuff – added to sinusoids of hepatic lobules –Plus, noxious conversions added to bile Intraperotineal
Pig liver (20X) C
PV – portal venule A – hepatic artery L – lymphatic duct B – bile duct S – sinusoids Limiting plate
Respiratory System Main functions: –Conducts air in/out –Exchange gasses w/blood – respiration –Includes mechanisms to prevent collapse of conducting tubes Bones Cartilage –Two major tube types: 1.Conducting pathway (nasal portion – lungs) 2.Respiration pathway (area of alveolar sacs)
Conducting Pathway Specialized lining of epithelium –“respiratory” epithelium that changes with arborization –Pseudostratified ciliated columnar epithelium With goblet cells – secrete lots of mucus –Cilia beat in one direction: Above pharynx – beat downwards Below pharynx – beat upwards Mucocilary escalator Mucus moved throughout passageway – trap dust
Conducting Pathway (cont.) Blood vessels – warm and moisten air Trachea (main passageway): –Contains C-shaped rings in adventitia R,L primary bronchi (enter lungs) –Same as trachea –Cartilage becomes reduced in bronchi of lungs –Epithelium – begin with pseudostrat ciliated to ciliated columnar Bronchioles –Epithelium – ciliated cuboidal to non-ciliated simple squamous Terminal bronchioles Respiratory bronchioles – start of the respiratory pathway Decrease in cartilage, glands, goblet cells height of epithelium Increase in smooth muscle and elastic tissue Extrapulmonary- Intrapulmonary-
Drawings of gas exchange
Trachea ls E – epithelium LP – lamina propria SM – submucosa F – fibroelastic tissue
Primary bronchus E – epithelium LP – lamina propria M – smooth muscle G – seromucous glands C – cartilage Goblet Cells in epith.