Digestion Continued Pancreas and Liver Respiration Histology 14 Digestion Continued Pancreas and Liver Respiration

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Large Intestine (generic) Principal functions: Recovery of HOH and salts from feces 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 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. 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 Rectum and Anal Canal: Waste material (feces) moves into this region and is expelled through the anus.

Large Intestine

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.

Recto-anal junction

Section Epithelium Cell types in E. Other features Esophagus Stratified squamous Squamous Submucosal glands Gradation of muscle Body / fundus Glandular – straight tubular Surface mucous cells Neck mucous cells Parietal cells Chief (peptic) cells Lymphoid sparse no aggregates Pylorus Glandular – coiled, branched tubular Mucous cells Occasional parietal Duodenum Glandular with villi and crypts of Lieberkühn Enterocytes with microvilli Goblet Cells Paneth Cells Brunner’s Glands Jejunum / ileum Peyer’s patches Colon / rectum Glandular – straight Goblet cells Absorptive cells Teniae coli Appendix Glandular – straight crypts Tall columnar cells Prominent lymphoid aggregates Anus Absorptive and goblet Squamous cells Colums of Morgagni Paneth Cells – lysozyme cells in bottom of crypts of lieberkuhn Colums of Morgagni – longitudinal folds in colon (non-distended) Peyer’s patches – lymphoid aggregates in colon Brunner’s glands – another name for the glands at the bottom of the crypts of Leiberkuhn in the duodenum Enterocytes – cells of epithelium

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

Central lumen Intercalated duct Intralobular ducts Interlobular ducts Pancreatic duct Ampulla of Vater Duodenum

Pancreas (45x)

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

Human (20X)

PV – portal venule A – hepatic artery L – lymphatic duct B – bile duct S – sinusoids Limiting plate Limiting plate – specialized hepatocytes surrounding the portal tract (triad)

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: Conducting pathway (nasal portion – lungs) 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 xs

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.

Bronchiole V – vein M – sm. Muscle

Terminal portion of respiratory tree T – terminal bronchiole R – respiratory bronchiole V – pulmonary vessel AD – alveolar duct AS – alveolar sac A - alveolus