Lab 8: Lymphatic, Digestive, Respiratory, Urinary, & Reproductive System Histology

Lymphatic System Histology

• the lymphatic system returns fluids that have leaked from vessels back into blood via lymphatic vessels, lymph, and lymph nodes

• lymphoid organs and tissues house phagocytic cells and lymphocytes that play a role in the body’s defense mechanisms and resistance against disease

• two major groups of lymphatic structures occur in connective tissues: encapsulated lymph organs and diffuse lymphoid organs

• the encapsulated lymph organs include lymph nodes, the thymus gland, and the spleen

• each encapsulated organ is separated from the surrounding connective tissue by a fibrous capsule

• diffuse lymphoid tissues do not have a defined boundary that separates them from the connective tissue and this type of lymphatic tissue is found in virtually every body organ

Lymphatic System Histology 2

• as lymph passes through a lymph node, phagocytes remove microbes, debris, and other antigens

• each lymph node is encased in a dense connective tissue capsule

• lymph nodes are scattered throughout the lymphatic system with a high concentration in the upper limbs and in the axillary and cervical regions

• the spleen is the largest lymphatic organ in the body and is located lateral to the stomach

• a capsule surrounds the spleen and protects the underlying tissue of red and white pulp

• the color of the red pulp is due to the blood that filters through; white pulp appears blue due to the lymphocyte nuclei stains

• as blood flows through the red pulp, free and fixed phagocytes in the pulp remove abnormal red blood cells and other antigens from the blood

• upon exposure to antigens, the lymphocytes of the white pulp become sensitized to them and produce antibiotics to counteract them

• blood drains from the sinuses of the red pulp to eventually mepty into the splenic vein

Figure 1, Lymph vessel valve at 40x

flow of lymph between lymph nodes and/or other lymphatic organs (i.e., spleen, tonsils, etc.) relies largely on a combination of skeletal muscular contraction and one-way valves to prevent retrograde flow

what is 1?

valve

what is 2?

valve leaflets

what is 3?

lymphatic vessel

Figure 2. lymph node at 100x

lymph is made from extracellular fluid that has entered lymphatic vessels. further components of lymph (i.e., leukocytes, etc.) are then added by the lymphatic organs. this slide shows lymph follicles within a lymph node. lymph nodes are bean-shaped lymphatic organs connected by a vast network of lymphatic vessels. the lymphatic system functions to collect and filter the lymph and is also teeming with macrophages, T cells, and B cells. each lymph follicle within each lymph node is an active center for B cells mitosis. dendritic cells, phagocytic cells that eventually make their way to the stratum spinosum of the epidermis, are also closely associated with these follicles. dendritic cells capture antigens and bring them back to the lymph nodes

what is 1?

capsule

what is 2?

germinal center of lymph follicle

what is 3?

medullary sinus

what is 4?

medullary cords

Figure 3. lingual tonsil at 100x

tonsils are collections of lymphatic tissue associated with the inside of the throat, specifically located at the base of the tongue, the back of the mouth, and the back of the nasopharynx. follicles of the tonsil function similarly to those of the lymph nodes. within the follicles are lighter stained germinal centers, which house proliferating B cells

what is 1?

adipose

what is 2?

germinal center

what is 3?

glossal muscle

what is 4?

mucous glands

Figure 4. palatine tonsil at 100x

palatine tonsils have several lymphoid nodules with numerous germinal centers. nodules are covered with stratified squamous epithelium and invaginate at places into tonsillar crypts

what is 1?

crypt

what is 2?

stratified squamous epithelium

what is 3?

septa

what is 4?

germinal center

Figure 5. thymus at 100x

the thymus initiates the development of immunocompetent T cells. in adulthood, the thymus degenerates. hassall’s corpuscles are a diagnostic feature of the thymus and are sites that accumulate dead T cells, but are also involved in the development of regulatory T cells that help prevent autoimmune response

what is 1?

Hassal’s corpuscle

Figure 6. spleen at 40x

the spleen is located on the left upper side of the abdominal cavity, below the diaphragm. it functions as the largest encapsulated organ of the lymphatic system with many macrophages and lymphocytes, but it also multi-tasks in entrapment and destruction of old erythrocytes and platelets. histologically, regions in which erythrocyte destruction is active are characterized as red pulp and regions where lymphocytes are concentrated are designated white pulp

what is 1?

red pulp

what is 2?

white pulp

what is 3?

arteriole

Figure 7. Hodgkin’s granuloma at 400x

Hodgkin’s granuloma is a cancer of the lymphatic system. untreated cancerous overgrowth can lead to the breakdown of both the splenic red and white pulp. Hodgkin’s disease used to have an invariably terminal outcome, but chemotherapeutic advances have vastly improved the prognosis. Reed-Sternberg cells are characteristic of Hodgkin’s disease and are derived from B lymphocytes (considered crippled germinal center B cells), meaning they have not undergone hypermutation to express their antibody. seen against a sea of B cells, they give the tissue a moth-eaten appearance

what is 1?

Reed-Sternberg cell

Figure 8a. illustration showing the differences between the parts of the digestive system. note the layers of the small intestine

what is 1?

serosa

what is 2?

muscularis

what is 3?

submucosa

what is 4?

mucosa

Figure 8b. illustration of the anatomical differences of the small and large intestines

Figure 9a. lip at 40x, Figure 9b. lip at 100x

the epidermis covering the anterior surface of the orbicularis oris muscle(used to purse the lips) defines the lips exteriorly. the skin of the lip is covered with poorly keratinized and pigmented epithelium allowing circulating blood to show more extensively beneath the surface. thusly, lips tend to appear redder than the surrounding skin. note the labial glands which are seromucous salivary glands associated with the lips. sebaceous (oil) glands are also present

what is 1?

orbicularis oris muscle

what is 2?

sebaceous gland

what is 3?

hair follicle*

*a hair follicle is the sheath of connective tissue and cells that surrounds the hair root

what is 4?

labial gland

what is 5?

orbicularis oris muscle

Figure 10a. taste buds at 40x, Figure 10b. taste bud at 400x

taste buds are clusters of encapsulated gustatory receptor cells located mostly on the surface of the tongue. the taste buds are concentrated on the surface of peg-leg like projections called papillae. Figure 10b is a section through a taste bud on the lateral surface of a vallate papilla. the taste bud encloses receptor cells that are aligned perpendicular to the free surface of the epithelial covering. gustatory epithelial cells are the receptor cells for taste while the basal epithelial cells are stem cells that divide to produce new gustatory epithelial cells. support cells are also present amongst the gustatory and basal epithelial cells

what is 1?

papillae

what is 2?

taste bud

what is 3?

excretory ducts of Von Ebner glands

what is 4?

lamina propria

what is 5?

skeletal muscle (of the tongue)

what is 6?

taste hairs (microvilli)

what is 7?

taste pore

what is 8?

gustatory epithelial cells

what is 9?

basal epithelial cells

what is 10?

connective tissue of lamina propria

what is 11?

epithelium of tongue

Figure 11. illustration of the tooth, Figure 12. tooth at 40x

teeth shear and masticate (mash up) food in the oral cavity. adult teeth can be divided into the part above the gum line (gingival margin) called the crown, followed by the neck, just above the alveolar margin, and the root, which is imbedded below the alveolar margin. the outer surfaces of teeth are plated with enamel, which is the hardest tissue of the body- even harder than bone. below the enamel is the thick layer of dentin, which makes up the bulk of the tooth. dentin is similar to bone and is manufactured by the odontoblasts. the pulp is the soft inner core region containing the blood and nerve supply of the tooth

what is 1?

crown

what is 2?

root

what is 3?

enamel

what is 4?

dentin

what is 5?

dental pulp

what is 6?

neck

what is 7?

gingiva

what is 8?

root canal

what is 9?

periodontal ligament

what is 10?

cementum

what is 11?

nerves and blood vessels

what is 12?

odontoblasts

Figure 13. esophagus at 40x