Histology 14

Digestion Continued

Pancreas and Liver

Respiration

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Large Intestine (generic)

• Principal functions:1. Recovery of HOH and salts from feces2. 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.

Large Intestine

Long section of the colon (4x)

Long section of colon (100x)2 main cell types:

1. goblet cells2. 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

Lymphoid sparse no aggregates

Duodenum Glandular with villi and crypts of Lieberkühn

Enterocytes with microvilli

Goblet Cells

Paneth Cells

Brunner’s Glands

Jejunum / ileum Glandular with villi and crypts of Lieberkühn

Enterocytes with microvilli

Goblet Cells

Paneth Cells

Peyer’s patches

Colon / rectum Glandular – straight Goblet cells

Absorptive cells

Teniae coli

Appendix Glandular – straight crypts Goblet cells

Tall columnar cells

Prominent lymphoid aggregates

Anus Glandular – 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 lumen2. Intercalated duct3. Intralobular ducts4. Interlobular ducts5. Pancreatic duct6. Ampulla of Vater7. 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

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

Mucocilaryescalator

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