Lymphatic System
A. Lymphocytes
1. white blood cells
a) develop from a hematopoietic stem cell
b) involved in immunity
2. natural killer cells
a) large lymphocytes that attack and destroy bacteria, transplanted tissues, and host cells that have become infected with viruses or have turned cancerous.
B cells (B lymphocytes)
a) lymphocytes that differentiate into plasma cells and mature in bone marrow
b) plasma cells
c) memory B cells
i. activated B cells that do not immediately differentiate into plasma cells. Can execute a quick secondary response when reexposed to the antigen that activated them initially.
T cells (T lymphocytes)
a) lymphocytes that mature in the thymus
b) helper T cells
i.
c) cytotoxic T cells
i.
d) memory T cells
B. Fluid, Tissues, Ducts, Glands, and Organs
1. Lymph/ lymphatic fluid
a) colorless fluid (red blood cells add color and it does not have those)
b) excess interstitial fluid that contains white blood cells
c) formed by filtration out of the blood capillaries into the lymphatic system
Lymphatic capillaries
a) similar to blood capillaries
b) permeable and contain valves
c) collect excess interstitial fluid
lymphatic vessels
a) similar to blood vessels
b drainage to vessels
c) function= transport of lymph, which includes excess interstitial fluid, proteins, and waste products back to the bloodstream.
lymph nodes
a) formed by lymph tissue (reticular cells and endothelium)
b) contain phagocytic cells
c) function= important for filtering lymph fluid and trapping pathogens, thereby playing a crucial role in the immune response.
5. lymphatic ducts
a) formed from lymphatic vessels that merge together
b) right lymphatic duct
i. right thoracic duct
ii. drains the upper right quadrant of the body
c) left thoracic duct
i. drains the rest of the body (thoracic trunks are larger)
6. bone marrow
a) red bone marrow
i. a primary lymphoid organ where B and T lymphocytes become immunocompetent
ii. function (s)= serves as site for hematopoiesis (blood formation) and immunity.
b) yellow bone marrow
i. made from adipose tissue
ii. functions (s)= provides storage of fat
7. adenoids
a) a patch of tissue located in the back of the nasal cavity
interstitial fluid> lymphatic capillaries> lymphatic vessels> lymphatic trunks> right and left thoracic ducts> subclavian veins> superior vena cava (largest) > bloodstream
tonsils
a) lymphoid organs
b) pharyngeal, lingual, palatine, and tubal tonsils
c) function (s)= guard against ingested and inhaled pathogens
thymus gland
a) located under the superior portion of the sternum
b) part of the endocrine system
c) function (s) = trains and matures T cells so they can fight infections without attacking the tissues of the body.
Peyer’s patches
a) large clusters of lymphoid follicles
b) located in the small intestine (part of the digestive system as well)
i. distal portion
c) functions= acts as an immune defense center in lower small intestine, detecting microbes and activating immune cells.
11. spleen
a) function=stabilizes blood volume, stores monocytes, produces blood cells in the fetus but continues to do so in adults during extreme anemia.
D. Terms
1) mastication
a) the chewing of food
2. deglutition
a) the process of swallowing food
3. bolus
a) a soft mass of chewed food mixed with enzymes and mucus that is ready to be swallowed
4. chyme
a) an acidic, soupy or pasty mixture of semi digested food
5. teeth
a) incisors, canines, pre-molars, and molars
6. esophagus
a) a long, hollow tube that is made of smooth muscle
b) brings food to the stomach
7. peristalsis
a) a wave of constriction traveling along a tubular organ such as the esophagus to ureter, to propel its contents
E. The Stomach
1. gastric pits
a) folds of the inner surface of the stomach
b) the openings of the gastric glands
2. gastric glands
a) glands in the lining of the stomach (gastric mucosa)
b) contain cells that secrete various substances
3. mucosa/ mucous membrane
a) lamina propria
i. layer of loose connective tissue beneath the epithelial layer of the mucosa
ii. Holds blood vessels, nerves, and lymphatic vessels that support the mucosal layer and facilitate nutrient absorption and immune function.
b) muscularis mucosa
4. muscularis mucosa
a) circular layer
b) longitudinal layer
5. submucosa
a) a thicker layer of loose connective tissue containing blood vessels and lymphatics, a nerve plexus, and in some places, glands that secrete lubricating mucus into the lumen
6. muscularis externa
a) longitudinal layer
b) circular layer
c) oblique layer
7. serosa
a) a thin layer of areolar tissue topped by simple squamous mesothelium
8. gastric rugae
a) conspicuous longitudinal wrinkles that form as the stomach empties
9. pyloric sphincter/ valve
a) a thick ring of smooth muscle that surrounds the pylorus and regulates the passage of chyme into the duodenum
10. cardiac glands
a) simple tubular glands near the junction of the esophagus and stomach that protect the esophagus and stomach lining from acid
11. pyloric glands
a) Protects the pyloric lining from acidic chyme, controls stomach acid level through gastrin and somatostatin, and regulates release of chyme.
12. gastric gland cells
a) chief cells
i. the majority type of cell in an organ or tissues; secrete the enzymes gastric lipase and pepsinogen
ii. take up the lower half of the gastric glands but are absent from cardiac and pyloric glands.
b) mucous neck cells
i. secretes mucus
c) parietal cells
i. Found mostly in gastric glands, but a few occur in the pyloric gland
ii. They secrete hydrochloric acid, intrinsic factor, and an appetite-stimulating hormone called ghrelin.
d. enteroendocrine cells
i. gastrin= stimulates gastric glands to secrete HCI and enzymes; stimulates intestinal motility; relaxes ileal papilla
ii. histamine= stimulates HCI secretion
iii. somatostatin= stimulates gastric motility
F. Small Intestine
1. mucosa
a) consists of simple columnar epithelium
2. muscularis mucosa
3. submucosa
4. muscularis externa
a) longitudinal layer and circular layer
5. serosa
6. circular folds
a) located in the mucosa and submucosa
b) function= slow the progress of the chyme and make it flow on a spiral path, increasing contact with the mucous and promoting more thorough mixture and nutrient absorption.
7. villi
a) fingerlike projections of the mucosa
b) function= joined by tight junctions that prevent digestive enzymes from seeping between them and eroding underlying tissue.
8. microvilli
a) extension of the cell membrane of enterocytes; forms the brush border
b) function= maximizes nutrient absorption in the small intestine.
9. enterocytes
a) cells in the villi of the small intestine
b) function= absorb nutrients from food and move them into the bloodstream or lymphatic system
10. goblet cells
a) cells in the villi of the small intestine
b) function= secrete mucus
11, lacteal
a) lymphatic capillary
b) function= carries absorbed fats from the small intestine to the rest of the body.
12. intestinal crypts
a) tubular glands
13. intestinal juice
a) finishes breaking down nutrients to be absorbed into the bloodstream.
14. ileocecal valve
a) controls movement between the small and large intestines and helps prevent infection by regulating the flow of digestive materials and bacteria.
G. Large Intestine
1. mucosa
a) consists of simple columnar epithelium
2. muscularis mucosa
3. submucosa
4. muscularis externa
a) longitudinal layer and circular layer
5. serosa
6. intestinal crypts
a) deeper structures than those of the small intestine
b) goblet cells
i. epithelial cells that produce and secrete mucus
7. gut microbiome/microbiota
a) 200 g and over 1.000 species of bacteria, yeasts, viruses, and other microorganisms reside in the gut, playing essential roles in digestion, immunity, and overall health.
b) Influence metabolic processes through mutually beneficial relationships
8. haustral contractions
a) the most common type of colonic motility which occurs every 30 minutes and is characterized by localized contractions that allow for mixing and segmentation of the intestinal contents.
9. mass movements= occur every 15 minutes and move residue several centimeters at a time and is triggered by the gastrocolic and duodenocolic reflexes.
H. Structures
1. greater omentum
a) part of the body’s first line of defense against toxins and infections that helps to filter lymph fluid and contains clusters of lymph nodes.
2. lesser omentum
a) structural support and serving as a pathway for blood vessels and ducts.
3. anus (large intestine)
a) providing a crucial role in the elimination of waste and the absorption of electrolytes and water.
4. rectum (large intestine)
a) stores feces until the body is ready to eliminate it.
5. internal sphincter (large intestine)
a) composed of smooth muscle of the muscularis externa
6. external sphincter (large intestine)
a) composed of skeletal muscle of the pelvic diaphragm
I. Accessory Organs
1. liver
a) produces and secretes bile
2. gallbladder
a) stores and releases bile
3. pancreas
a) pancreatic juice
i. an alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and electrolytes that aids in the digestion and neutralization of stomach acid.
b) insulin
i. a hormone produced by the pancreas that regulates blood glucose levels by promoting the uptake of glucose into cells.
c) glucagon
i. Is released by the endocrine part of the pancreas.
d) trypsinogen
i. becomes tyrypsin, which digests protein
e) chymotrypsinogen
i. becomes chymotrypsin, which digests protein.
f) procarboxypeptidase
i. becomes carboxypeptidase, which hydrolyzes the terminal amino acid from the carboxyl end of small peptides.