Histology 14

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					 Histology 14

Digestion Continued
Pancreas and Liver
1. Strike
2. Extra Credit
3. Research
           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
•       No villi
•       Intestinal glands – mucus
    –      Crypts of Lieberkühn
•       Surface epithelia – mostly goblet cells and absorptive
•       Specialized muscularis externa
    –      Longitudinal muscle is separated into three independent
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
     –     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)
                           2 main cell types:
                                   1. goblet cells
Long section of colon (100x)       2. absorptive cells
• Sulculation caused by taeniae coli down to
  the anus – then continuous sheet of
  longitudinal muscle.
• 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          Surface mucous cells          Lymphoid sparse no
                    tubular                       Neck mucous cells             aggregates
                                                  Parietal cells
                                                  Chief (peptic) cells
Pylorus             Glandular – coiled,           Mucous cells                  Lymphoid sparse no
                    branched tubular              Occasional parietal           aggregates

Duodenum            Glandular with villi and      Enterocytes with microvilli   Brunner’s Glands
                    crypts of Lieberkühn          Goblet Cells
                                                  Paneth Cells

Jejunum / ileum     Glandular with villi and      Enterocytes with microvilli   Peyer’s patches
                    crypts of Lieberkühn          Goblet Cells
                                                  Paneth Cells

Colon / rectum      Glandular – straight          Goblet cells                  Teniae coli
                                                  Absorptive cells
Appendix            Glandular – straight crypts   Goblet cells                  Prominent lymphoid
                                                  Tall columnar cells           aggregates

Anus                Glandular – straight          Absorptive and goblet         Colums of Morgagni
                    Stratified squamous           Squamous cells
         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
Pancreas (45x)
Exocrine Acinus (8500x)
• 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
• Largest gland in body (1500g)
• Divided into 4 lobes (R, L, quadrate and
• 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
  – Pseudostratified ciliated columnar epithelium
     • With goblet cells – secrete lots of mucus
  – Cilia beat in one direction:
     • Above pharynx – beat downwards           Mucocilary
     • Below pharynx – beat upwards

      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                           • Extrapulmonary-
                                               • Intrapulmonary-
   – 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
• Increase in smooth muscle and elastic tissue
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
 • C – cartilage
 • Goblet Cells in epith.
• V – vein
• M – sm.
• Terminal portion of respiratory tree
    –   T – terminal bronchiole
    –   R – respiratory bronchiole
    –   V – pulmonary vessel
    –   AD – alveolar duct
    –   AS – alveolar sac
    –   A - alveolus

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