Chapter.20 Lymphatic System & lymphoid organs and tissues

Lymphatic System: returns fluids that have leaked from the blood vascular system back into the blood

3 Parts:
Network of lymphatic vessels
Lymph = fluid contained in those vessels
Lymph nodes - cleanse the lymph as it passes through them

Lymphatic vessels form a one way system in which lymph fluid flows only towards the heart.

when fluid pressure is greater then the pressure n the lymphatic capillary it will be drained toward the heart.

order questions? how does it flow from the lymphatic capillaries to the heart? or opposite way around.

The cistern chill collects lymph from the 2 larger lumbar trunks that drain the lower limbs & form the intestinal trunk that drains the digestive organs.

Lymphoid Organs & Tissues: provide the structural basis of the immune system

-House phagocytic cells & lymphocytes which play roles in the body defines mechanisms & resistance to disease. Ex- Spleen

Lymphatic Capillaries:
Weave btwn the tissue cells and blood capillaries in the loose CT of the body these vessels to be EXTREMELY permeable due to mini-valves.

Lymphatic Trunks: drain large areas of the body, named for the regions which they drain lymph

Lymphatic Ducts:
R Lymphatic Duct
-drains lymph from R upper limb & right side of head and thorax
2) Thoracic Duct much larger b/c receives lymph from the rest of the body

Lymph Transport:
Lymphatic vessels are low-pressure conduits
Use the same mechanisms that promote venous return in blood vessels to move the lymph
a)Milking action of active skeletal muscles
b)Pressure changes in the thorax during breathing
c)Valves to prevent back flow

Lymphoid Cells:

Agranulocytes:
4.Lymphocytes
Only 2% are found in blood, Most are in lymph tissue (lymph nodes, & spleen) Perform immune responses
Arise in red bone marrow & mature into one of two main types…

T lymphocytes (T cells)
Manages immune responses, attack & destroy infected cells
(mature in the thymus gland)
Give rise to:
Effector T Cells (cytotoxic T cells)- secrete cytotoxic agents that destroy virus invaded cells & cancer cells
b) Helper T Cells- secrete chemical messengers to activate T & B cells as well as macrophages
c) Regulatory T Cells-
“remember” antigen for rapid immune response 2nd encounter

2) B lymphocytes (B cells)
Protects body by producing plasma cells that secrete antibodies that mark antigens for destruction.
(mature in bone marrow)
Give rise to:
a)Plasma Cells- produce antibodies that will attach to foreign cells (antigens) & destroy them
b) Memory B Cells-
“remember” pathogens encountered and can have a rapid response if it is detected again

Antigens are anything that provokes an immune response.
-such as bacteria, their toxins
-viruses
-mismatched RBC
-cancer cells

Macrophages: play crucial role in body protection & immune response
-phagocytize foreign substances
-help to activate T cells

Lymphiod tissues:
-where we store our lymphocytes, and watch for problems
Functions:
Houses + provides a proliferation site for lymphocytes
Is an ideal surveillance vantage point for lymphocytes & macrophages

Types:

Diffuse lymphoid tissue: loose arrangement of lymphoid cells & some reticular fibres. Found in virtually every body organ

b) Lymphoid follicles/nodules:
Solid, spherical bodies consisting of tightly packed lymphoid cells & reticular fibers.-forms larger lymphoid organs -lymph nodes

Lymph Nodes:

2 functions:

1)Filtration:
Marcrophages in nodes remove and destroy microorganism and other debris in the lymph.

2) Immune system activation: sites where lymphocytes will encounter antigens & are activated to mount an attack against them

Lab exam question- what digestive role does the spleen have?

Spleen:
Largest lymphoid organ
Found on L side of abdominal cavity below the diaphragm
Provides a site for lymphocyte multiplication & immune surveillance & response
-stores blood platelets & monocytes for release into the blood
-site of erythrocyte production in the fetus

Extracting old/damaged blood cells and platelets from blood.
-its macrophages remove debris and foreign matter from blood

Histology:
White pulp
-where immune functions take place
-composed mostly of lymphocytes suspended on reticular fibers
B) Red Pulp
-where worn out RBC’s & blood borne pathogens are destroyed
-sontains large # of erythrocyte & macrophages that engulf them

what does the white and red pulp do in the spleen?

Thymus:
Found in the inferior neck region
Maturation site for T lymphocyte precursors
-Must be kept isolate from foreign antigens to prevent their premature activation
-There is a blood thymus barrier that keeps blood born antigens out of the thymus

Mucosa- Associated Lymphoid Tissue (Malt): is a set of distributed lymphoid tissues strategically located in mucous membranes throughout the body.

know all these organs

Tonsils: ring of lymphoid tissue around entrance to the pharynx
-gather & remove many of the pathogens entering the pharynx in food or inhaled air
**Include Palatine, lingual, pharyngeal and tubal tonsils! **

Palatine: ethier side at the posterior end of oral cavity

Lingual: base of tongue

Pharyngeal: posterior wall of the nasopharynx

Tubal: surround the opening of auditory tube into pharynxl

Peyer’s Patches: structurally similar to the tonsils
Located in wall of the distal portion of the small intestine

Appendix: tubular offshoot of the first part of large intes.
Destroys bacteria generates many “memory” lymphocytes from long-term immunity

Review!

LAB NOTES- Feb.2nd BLOOD

Must know: normal % of each type of WBC, know fncs of each type, know disease condition if % changes, normal hematocrit ( male and female) normal hemoglobin concentration (male/female) normal total: RBC (male/female)
-what condition would cause a increase or decrease
-normal total WBC count- what condition can cause increaser decrease
-normal clotting time

knowthe 2 subdivisions of dig. system give example of where you can find a fibrous suture

Anatomy : Digestive System -missing lots online

2 Major Sub-divisions:

Gastrointestinal Tract (GIT)
Mouth, pharynx, esophagus, stomach, small intestine, large intestine

2) Accessory Digestive Organs teeth, tongue, salivary glands, liver, gall bladder, pancreas

6 functions:
Ingestion
Secretion
Mixing & propulsion
Digestion (mechanical/ chemical)
Absorption
Defecation

HISTOLOGY
4 layers throughout entire digestive tract:

1)Mucosa (lines the lumen)
2)Submucosa - thick Areolar CT w/ Blood vessels, Lymph vessels, nerves and glands
3)Muscularis
4)Serosa (outside layer) CT & Simple squamous for protection

Serous Membranes of the GIT:
Lining abdominopelvic cavity = Parietal peritoneum
Covers organs = Visceral peritoneum

The space between the organs and the skin is called the …. cavity?
Peritoneal cavity! Filled w/ serous fluid - to lubricate

Folds of the peritoneum bind organs together & to abdominal wall. These folds include…
Mesentary:suspends s.i from posterior body wall.
Greater momentum: extends from greater curveture of stomach & drapes over intestines
Lesser omentum: from lesser curtain of stomach to liver
Falciform ligament: attaches liver to front body wall
Mesocolon: Suspends Large int. from back body wall

Regulation of Digestive Functions:
-Regulate GIT muscle motility & secretions
Control mechanisms - neural and endocrine
Endocrine control: various hormones
Neural control: involves Enteric NS & Autonomic NS
Sensory input to ENS & AND comes from chemoreceptors (detect chemical contents of pH of gut) & stretch receptors (detect distension of gut)
Enteric NS motor neurons are arranged in the gut wall as the:
-myenteric plexus (controls gut motility)
-submucosal plexus (controls GIT secretion of mucosa

Autonomic NS motor neurons can modify activity of the ENS or act directly on smooth muscle and glands
-in general parasympathetic nerve stimulation increases GIT activity (stimualte digestive motility & secretions) & sympathetic nerve stimulation decreases activity

Mouth (Oral/ Buccal Cavity):
-Hard & Soft palates allow breathing while chewing
-Non-keratinized stratified squamous epithelium
Tongue is composed of bundles of skeletal muscle covered by epithelium - manipulates food & initiates swallowing
Teeth are located in alveolar sockets of the mandible and maxilla - mechanically breakdown food

Salivary Glands (accessory organs) produce & secrete saliva into mouth - 3 types (parotid, sublingual & submandibular glands)
-Saliva: dissolves some ingested material for taste identification
-contains mucus to lubricate and form bolus
-contains salivary amylase - starts breakdown of starch to sugar
-contains lysozyme

PNS increases saliva secretion in response to touch/taste receptors, sight, though and smell of food

Pharynx:
Swallowing occurs:
-tongue pushes food against hard palate & bolus is forced into oropharynx
-receptors are stimulated that initiate swallowing reflex in medulla and pons
-soft palate and uvula rise and close off nasopharynx
-larynx elevates & epiglottis covers glottis and food/liquid passes through upper esophageal sphincter
-peristaltic contractions propel blus down
-lower esophageal sphincter opens

Esophagus:
Muscular tube - w/ nonkeratinized stratified squamous epithelium
Posterior to trachea
Alternating waves of contraction & relaxation propels bolus to stomach (called peristalsis)
-circular muscle fibers contract to constrict the wall & bolus is squeezed downward
-meanwhile below bolus, longitudinal fibres contract to shorten & expand the esophagus wall to receive the bolus

Stomach:
4 regions:
Cardia
Fundus
Body
Pylorus

Empty volume = 50ml
Capacity (full) = 1.5-2.5 L
Very distended = 4L

Mucosa = simple columnar epithelium
-forms gastric glands! With many cell types…
Mucus neck cell: produces protective mucus - protect stomach walls from HCl + pepsin
Parietal cells: produce HCl & intrinsic factor for Vitamin B12 absorption.
Chief cells: produce pepsinogen (inactive protein-digesting enzyme)
Enteroendocrine cells: G cells that secrete the hormone gastrin

Secrete 2-3L of gastric juice/day
Mucosa forms large folds when the stomach is empty called rugae - which allow it to distend
Muscularis has an inner oblique, middle circular and outer longitudinal smooth muscle layer
-extra oblique layer allows the stomach to compress, knead + twist

Stomach functions:
Storage & mixing
-mechanical digestion from peristaltic waves mixing food with secretions of gastric glands to form chyme

This begins protein digestion
-HCl activates pepsinogen to form pepsin
-proteins are broken down into peptides
Aborsb some water, ions, alcohol, drugs

Small Intestine:
Begins at pyloric sphincter & includes the duodenum, jejunum & ileum
Mucosa has a simple columnar epithelium w/ many goblet cells & deep crypts
Major area of digestion & absorption of nutrients - large surface area needed:
-presence of villi in mucosa
-presence of microvilli
-presence of picas circulates (permanent folds of the mucosa & submucosa)

Mucosa has several cell types:
Absorptive cells: absorb & digest nutrients
Produce enzymes
2. Goblet cells: produce mucus
3.Secretory cells: secrete intestinal juice
4.Paneth cells: secrete lysozyme
5. Enteroendocrine cells:
S cells secrete the hormone secretin ! CCK cells secrete cholecystokinin
S.I Functions:
1.Mechanical digestion
-segmentation mixes chyme w/ intestinal juice, pancreatic juice & bile
-circular smooth muscles alternately contracts and relaxes and chyme moves back and forth to mix
2.Completes carbohydrate, protein and lipid digestion
3.Aborbs 90% of nutrients cross epithelial cells to enter blood and lymph vessels in the villus
4.Peristaltic waves move chyme to ileocecal valve

Pancreas: accessory organ that lies inferior to the greater curvature of the stomach
Exocrine Gland (99%)(glandular cells) secrete pancreatic juice into small ducts — pancreatic duct — hepatopancreatic ampulla — duodenum

Secrete about 1.5L of alkaline pancreatic juice per day

& Endocrine gland (1%)