Thymus one of the few glands to shrink with age 70

Thymus
•
One of the few glands to shrink with age, 70 grams
to 3 grams
•
Contained within a capsule
•
Invaginations of the capsule are called trabeculae
and form thymic lobules just like the RLN
•
The dark outside layer is the cortex and where the
initial T cell programming occurs
•
The lighter center called the medulla is the final
program area for maturing pre-T cells occurs

Thymus continued
•
Other cells in the thymus include dendritic cells
derived from monocytes and act as antigen
presenting cells
•
Also epithelial cells function to secrete thymic
hormones to assist in T cell programming, and
form the framework of the thymus
•
Thymic corpuscles are located in the medulla
and manufacture keratohyaline and keratin of
unknown function

Spleen
•
Largest lymphatic organ
•
Also contains a capsule with trabeculae
•
In this case the outside layer is the stroma containing
reticular and fibroblast cells
•
The parenchyma contains the splenic artery of white pulp
that houses a high number of lymphocytes (B and T cells)
•
The splenic vein forms the red pulp containing RBCs,
macrophages for phagocytosis of old RBCs, and 1/3
rd
of all
the bodies platelets
•
Look up the word splenunculi

Non-specific disease defense mechanisms
•
AKA innate
•
First line of defense that is both physical and
chemical
•
Does not need programming centers

Normal microbiota
•
Takes up:
–
Space
–
Nutrients
–
Gases like oxygen
–
Vitamins
•
Release bacteriocins
–
The vast majority are toxic to other organisms such as
other microbes and of course humans
–
The few that are not toxic to humans can possibly be used
as antibiotics

Skin
•
Skin is a pressure vessel
•
Shedding completely every two weeks
•
Oil and sweat is bacteriostatic
•
The skin is waterproof
•
The skin is dead
•
Clotting stops bleeding but also entraps
microbes

Interesting facts
•
Microbes vary on area and person
•
Some are coccoid others are bacilli
•
Hand washing with antibacterial is a risk for
infection
•
8 hour to recolonize
•
Triclosan is a trichlorinated bi-phenolic

Eyes
•
We always cry
•
Drains into the acid pit
•
Tears flush
•
Tears also contain lysozyme
•
Lysozyme disrupts the formation of bacterial
cell walls undergoing division
•
Lysozyme is also found in saliva and mucous in
general

Ear wax
•
Cerumen is long chain fatty acids
•
Also an as yet unknown agent that is
bacteriostatic
•
Interesting note is that genetically people are
either hard of soft wax secretions

Gastrointestinal
•
Acid and alkaline environment
•
Many digestive enzymes also kill microbes
•
Initial microbiota is important
•
Oral antibiotics have made a mess of the
microbiota of a lot of people

Respiratory system
•
At a high risk: because the lungs are: living,
thin, high surface area, and exposed
•
Conchae AKA nasal turbinates
•
Mucous lined
•
Smart cilia
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Vibrissae
•
Epiglottis
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High number of RLNs and macrophages