9-15 Histology Lecture Notes PDF

The Integumentary System On-line reading: http://www.doctorc.net/Labs/Lab14/Lab14.htm http://www.doctorc.net/Labs/Lab15/Lab15.htm http://lifesci.dls.rutgers.edu/~babiarz/integ.htm Layers of the skin from superficial to deep (slides 2 ) 1....

The Integumentary System On-line reading: http://www.doctorc.net/Labs/Lab14/Lab14.htm http://www.doctorc.net/Labs/Lab15/Lab15.htm http://lifesci.dls.rutgers.edu/~babiarz/integ.htm Layers of the skin from superficial to deep (slides 2 ) 1. epidermis - surface layer >> epithelium 2. dermis - middle layer >> supports epidermis via blood vessels, nerves and epidermal appendages 3. hypodermis or subcutaneous layer - composed primarily of adipose tissue and loosely attaches skin to underlying structures epidermis 1. stratified squamous epithelium >> keratinized in superficial strata and varies in thickness among different regions of the body (slide 3) 2. types of cells A. keratinocytes - produce the protein keratin >> waterproofs skin (slide 4) (1) predominate cells B. melanocytes - spider-shaped cells of deeper epidermis that synthesizes the pigment melanin >> protects underlying structures from UV light (slide 5) (1) found in stratum basale >> appear as round nuclei with clear halo of cytoplasm with H&E (slide 6) C. Langerhans cells – macrophages >> most easily seen in stratum spinosum >> somewhat rounded nuclei with clear halo of cytoplasm in H&E (slide 7) 3. layers of the epidermis from deep to superficial (slide 8) A. stratum basale or stratum germnativum (1) separated from dermis by basement membrane >> layer close to blood supply 1  (2) keratinocytes exist as single layer of columnar cells >> mitotically active (3) melanocytes B. stratum spinosum or prickle cell layer (slide 9) (1) up to 8-10 cells in this layer (2) slight mitotic activity (3) cells become less viable superficial to this layer >> too far away from blood supply C stratum granulosum (slide 10) (1) thin layer 3-5 cells thick (2) keratinization begins here (3) upper cells of this layer begin to die and flatten out to eventually obtain squamous shape D. stratum lucidum - clear layer with keratinization continuing (1) only present in thick skin E. stratum corneum (1) most superficial layer (2) varied in thickness on different parts of the body (3) dead cells essentially bags of keratin (4) most superficial cells constantly being shed dermis 1. composed of loose and dense irregular connective tissue (slide 11) A. cells - mainly fibroblasts with occasional macrophages, lymphocytes, mast cells and other immune cells B. rich nerve, lymph and blood supply 2  2. subdivided into two layers (slide 12) A. papillary dermis - upper layer >> paler staining due to fewer fibers and more matrix B. reticular layer - larger and deeper layer >> darker staining due to abundance of large diameter collagen and elastic fibers (1) fibers important in skin strength and elasticity (2) adversely affected by UV light appendages and other specialized structures of the skin 1. hair - elongated columns of fused keritinized epithelial cells originating from a tubular evagination of the epidermis into the dermis >> growth occurs from bulb at base of follicle (slides 13 and 14) A. follicle of hair contains internal root sheath (epidermis origin) and external root sheath (dermis origin), each of which is composed of several distinct layers B. associated with sebaceous glands and arrector pili muscles (slide 15) 2. sweat glands and their associated ducts (slide 16) A. eccrine glands - cover most of the body but most concentrated in regions of thick skin >> thermoregulation (slide 17) (1) coiled tubular glands composed of eosinophilic cuboidal epithelium surrounding a central duct that serpentines its way to the surface B. apocrine glands - empty into hair shafts in axillary & anogenital regions >> secretions metabolized by microbes >> odor (slide 18) (1) tightly coiled tubular glands composed of eosinophilic cuboidal epithelium surrounding a central duct but surface is quite rough due to artifact >> do not secrete via apocrine mode 3  3. oil or sebaceous glands - simple or branched alveolar glands with a washed out appearance similar to adipose in standard histological preparations (slide 19) A. holocrine mode of secretion >> lumen filled with dead cells 4. structures involved in cutaneous sensation - different types of receptors for different types of stimuli A. free nerve endings - detect pain, temperature and itch (slide 20) B. Pacinian corpuscles - consists of modified Schwann cells that form lamellae around a central axon (slide 21) (1) detect pressure and vibration (2) located deep within reticular dermis or hypodermis (3) also found in other organs C. Meissner's corpuscles - encapsulated structure in which flattened Schwann cells produce a spiral orientation to the axon (slide 22) (1) located within dermal papillae >> detect fine touch D. Merkel cells - fine touch receptors that have the ability to adapt over time (1) located in stratum basale or just deep to basement membrane (slide 23) E. nerve endings that form tubular nets surrounding hair follicles >> touch detectors (slide 24) Online slide review: http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/skin_glands.htm Virtual microscope: http://www.histologyguide.org/slidebox/11-skin.html The Cardiovascular System On-line reading: http://www.doctorc.net/Labs/Lab12a/Lab12a.htm http://www.doctorc.net/Labs/Lab12b/Lab12b.htm http://lifesci.dls.rutgers.edu/~babiarz/BVs.htm histology of the heart 4  1. layers (slide 2) A. endocardium – inner layer of simple squamous epithelia and a supporting layer of fine connective tissue (slide 3) B. myocardium – middle layer composed of cardiac muscle (slide 4) (1) thickest of the three layers a. atria – low pressure >> thinnest myocardium b. left ventricle – highest pressure >> thickest myocardium (2) myocytes separated by a rich capillary network C. epicardium – outermost layer >> synonamous with viseceral pericardium (slide 5) (1) composed of a simple squamous epithelial covering >> underlying connective tissue contains copious amounts of adipose 2. other histological features of the heart A. papillary muscles – provide tension for chordae tendinae (slide 6) B. chordae tendinae – collagenous and elastic structures that prevent prolapse of atrioventricular valves >> occasional seen in histological sections C. heart valves – prevent backflow within the heart (slide 7) (1) lamina fibrosa – central collagenous plate (2) elastic fibers prominent on atrial surface (3) covered by endocardium on both surfaces D. only a few components of the cardiac conduction system are visible histologically (slide 8) 5  (1) sinoatrial and atrioventricular nodes - composed of irregular twirling of small fibers that lack intercalated discs and are embedded in collagenous connective tissue (2) Purkinje cells – modified myocytes that act as terminal branches of cardiac conduction system in ventricles a. located just deep to endocardium (slide 9) b. appearance i. cells typically larger than myocytes and often binucleated ii. less myofibrils iii. large glycogen stores surrounding nucleus >> removed during histological processing >> clear area surrounding nucleus blood vessels 1. basic layers (slide10) A. tunica intima – innermost layer composed of endothelial cells with a thin underlying layer of connective tissue B. tunica media – middle layer composed of circular oriented smooth muscle cells C. tunica adventicia or tunica externa– outermost layer composed of connective tissue >> usually merges with surrounding connective tiisue of organ 2. arteries - carry blood from the heart to other parts of the body A. elastic arteries - largest arteries near the heart that contain circumferential sheets and finestrated sheets of elastic fibers primarily within tunica media (slide 11) (1) tunica media and tunica externa highly invested with blood vessels >> vasa vasorum 6  B. muscular arteries (distributing arteries) - derived as major branches off elastic arteries to supply organs and the extremities (slide 12) (1) muscle important in constriction/dilation of the artery that allows direct role in controlling flow of blood >> smooth muscle of tunica media responds to nervous, hormonal and local metabolite stimuli (2) histology - three tunicas plus internal and external elastic laminas very distinct (slide 13) C. arterioles - most distal branches of arterial system in which smooth muscle layer is still continuous (slide 14) (1) most important vessel in controlling blood flow/pressure (2) metarterioles - have small lumenal diameter (approximate size of capillary) and only occasional and scattered smooth muscle cells (slide 15) a. important in controlling blood flow through capillaries 3. capillaries - smallest blood vessels of circulatory system with thinnest walls >> site of all exchange (slide 16) A. consist of endothelium and basal lamina >> wall only one cell thick B. pericyte – cells associated with small vessels >> contractile function + maintain vessel integrity C. types of capillaries (slide 17) (1) continuous - endothelia forms complete lining without any defects >> most common type (2) finestrated - endothelia processes minute pores that renders capillary wall more permeable >> found in GI tract, endocrine glands, kidney, choroid plexus (slide 18) (3) sinusoids - channels that are larger than normal capillaries and have a highly finestrated basal lamina >> 7  found in liver, spleen, bone marrow and some endocrine glands (slide 19) 4. small venules (slide 20) A. post capillary venules – receive blood from multiple capillaries >> endothelium with surrounding pericytes (1) endothelial cells lack junctional complexes >> site of most WBC migration into surrounding connective tissue (slide 21) B. collecting venules – similar in structure to post capillary venules but larger with multiple layers of pericytes C. muscular venules – slightly larger than collecting venules >> smooth muscle fibers replace pericytes 5.veins (slide 22) A. recognized by large lumen and thin walls B. tunicas less distinctly demarcated C. low pressure system >> need for valves in extermities to return blood to the heart (slide 23) lymphatic ystem 1. blind end system of vessels that parallels capillary and venous side of the cardiovascular system (slide 24) 2. function - drains surplus fluid from tissues, immunolgically screens it, and returns it to the blood (slide 25) 3. lymphatic vessels - lymph capillaries and veins A. not pumped by the heart (1) thin walled vessels (slide 26) (2) require incidental compression of skeletal muscles and valves to facilitate movement of lymph 8 Online slide review: http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/blood_vessels.htm Virtual microscope: http://www.histologyguide.org/slidebox/09-cardiovascular-system.html Lymphoid and Immune System On-line reading: http://www.doctorc.net/Labs/Lab13/Lab13.htm http://lifesci.dls.rutgers.edu/~babiarz/lympho.htm lymphoid tissue - morphologically homogenous but functionally heterogeneous population of WBCs and WBC precursors suspended within a reticular matrix 1. locations (slide 2) A. tonsils B. lymph nodes C. spleen D. thymus E. diffuse aggregates throughout respiratory and GI systems (ex. Peyer's patches) 2. represents storehouse of immune system cells that can respond to antigenic activation and disperse rapidly to other locations in the body via either lymph or blood vessels A. macrophages - most are of bone marrow origin B. lymphocytes C. plasma cells D. neutrophils and eosinophils >> migrate into lymphoid tissues during time of active infection organization of lymphoid tissue 1. diffuse lymphoid tissue - occurs in the connective tissue deep to the epithelium of the GI and respiratory tracts (slide 3) A. also present in the stroma of virtually all internal organs when infection is present 9  2. nodular lymphoid tissue - dense spherical aggregates of lymphocytes typically located among diffuse lymphoid tissue (slide 4) A. nonpermanent structures >> come and go according to immunolgical needs B. germinal centers - lightly staining centers of some nodules (1) represent active proliferation of B lymphocytes lymphoid organs 1. primary lymphoid organs - responsible for initial differentiation of B and T lymphocytes from precursors A. thymus – site of T lymphocyte development (slide 5) (1) located in superior thoracic cavity (2) seeds T lymphocytes to other locations throughout body beginning prior to birth and then undergoes involution >> replaced with fat by late teenage years (3) histology (slide 6) a. encapsulated with incomplete partitions called trabeculae forming lobules b. cortex - outer dark staining region >> dense population of proliferating T cells that are differentiating into different subtypes i. cells move toward medulla during development ii. macrophages in deeper portions of cortex >> remove T-cells that have not differentiated properly c. medulla - inner light staining region >> contains higher concentration of reticular cells and epitheliocytes (slide 7) 10  i. Hassall's corpuscles - degeneration and concentric layering of epitheliocytes d. involution – thymus degenerates at T cells seeded to other locations in body (slide 8) B. bursa equivalent = bone marrow >> original source of B lymphocytes 2. secondary lymphoid organs - seeded with appropriate cells from primary lymphoid organs >> site of continuing cell production and function in the adult A. gut associated lymphoid tissue (GALT) - connective tissue layer of GI highly infiltrated with lymphocytes >> form diffuse and nodular aggregates in some areas (1) prominent in ileum (Peyer's patches) and appendix (slide 9) (2) similar aggregates within connective tissue of respiratory tract (MALT) B. lymph nodes - small bean-shaped organs found at certain locations along lymphatic vessels (1) structure (slide 10) a. internal scaffolding composed of reticular connective tissue b. dense irregular connective tissue capsule forms partial partitions c. subcapuslar sinus (slide 11) d. cortex filled with diffuse and nodular lymphoid tissue e. medulla contains medullary cords and sinuses (slide 12) f. several afferent lymphatic vessels enter lymph node at different locations >> single efferent lymphatic vessel exits at hilum (slide 13) 11  (2) function a. lymph from afferent vessels empties into subcapsular sinus and then into sinusoids between medullary cords for immunological screening (slide 14) b. high endothelial venules – allow lyphoid cells to exit circulation >> cells which do not recognize antigen remain in lymph and exit node within hours (slide 15) c. antigen recognized >> stimulates active mitosis of B-cells generating a nodule with a germinal center d. T-cells primarilly located in regions between nodules (slide 16) C. spleen - largest lymphoid organ of the body >> often conceptualized as a large lymph node (slide 17) (1) functions >> filters blood a. immunologically screens blood b. macrophages remove senescent RBCs c. blood reservoir (2) histological structure (slide 18) a. connective tissue capsule that gives rise to nonpartitioning trabeculae b. reticular fiber scaffolding c. bulk composed of a soft mushy parenchyma >> pulp i. red pulp - lymphocytes plus sinusoids filled with blood ii. white pulp - composed primarily of lymphoid tissue (3) vascular anatomy and function (slide 19) 12  a. splenic artery >> trabecular arteries >> central arteries i. tunica adventicia of central arteries assumes composition of reticular connective tissue >> infiltrated by lymphocytes (white pulp) to be known as the periarteriole lymphatic sheath (PAL) c. central arteries >> pencillary arterioles >> sheathed capillaries i. sheathed capillaries – blind ended vessels not composed of endothelial cells >> walls composed of layers of macrophages ii. blood transverses through macrophage walls into open circulation of red pulp >> direct interaction of blood with lyphoid cells allows immunological screening plus removal of scenescent RBCs d. open circulation >> red pulp sinusoids >> splenic veins D. tonsils - form a ring around the opening of the pharynx (slide 20) (1) names of clinically important tonsils a. palatine tonsils b. lingual tonsils c. median pharyngeal tonsil >> enlarged = adenoids (2) histology (slide 21) a. covering epithelia highly infolded >> crypts i. thought to be important in generating a large immunological library b. diffuse and nodular lymphoid tissue within crypts 13  c. hemicapsule – dense irregular connective tissue deep to tonsils d. nodules greatly enlarged with germinal centers during infection >> swollen or sore throat Online slide review: Virtual microscope: http://www.histologyguide.org/slidebox/10-lymphoid-system.html Respiratory System On-line reading: http://www.doctorc.net/Labs/Lab25/lab25.htm http://lifesci.dls.rutgers.edu/~babiarz/respir.htm introduction to the respiratory system - branching system of air passageways with approximately 80 m 2 of surface area >> main function is to supply oxygen to the blood and eliminate carbon dioxide >> two main divisions to system (slide 2) 1. conducting portion - branching system of air passageways A. functions (1) main function - to admit a maximum volume of air through a narrow inlet and a minimal volume of passageways (2) minor functions a. removing particulate material from air b. adjusting temperature and moisture content of incoming air c. voice box B. components - nasal cavities & paranasal sinuses >> pharynx >> larnyx >> trachea >>>> bronchi >>>> bronchioles >>>> terminal bronchioles (slide 3) C. general histology - layed tubes consisting of conducting mucosa (epithelia plus lamina propria, submucosa and 14  muscularis mucosa layers >> all layers not always present (slide 4) 2. respiratory portion - represents approximmately 40% of total respiratory system surface area >> functions to allow mutual gas exchange between the air and the blood A. components - respiratory bronchioles >>>> alveolar ducts >>>> alveolar sacs >>>> alveoli (slide 5) B. approximately 25 generations of branching to reach alveoli conducting portion - lined with conducting mucosa >> pseudostratified epithelium (goblet cells, ciliated cells and basal cells) with a thin, highly glandular loose irregular connective tissue called the lamina propria 1. histology of the nasal cavities, paranasal sinuses and pharynx (slide 6) A. begins as stratified squamous epithelium at entrance fo nasal passageways >> eventually becomes pseudostratified with abundant goblet cells B. lamina propria lies dierctly upon underlying structures (ie. bone, cartilage or muscle) (1) contains abundant serous and mucous glands (2) aggregates of lymphoid nodules (3) abundant thin walled blood vessels called cavernous or erectile tissue >> each side alternately becomes engourged with blood thereby only allowing breathing through the oppposite side (4) olfactory mucosa (slide 7) a. located in roof of nasal cavity b. cell types i. basal cells ii. olfactory receptor cells – bipolar neurons which end in olfactory knob >> modifed and 15  nonmotile cilia provide for interaction with odiferous molecules iii. sustenacular cells – tall ciliated columnar cells - steriocilia form a tangled mat >> intermingled with olfactory cilia - form junction complexes on lateral apical surface with olfactory cells >> provide structural and physiological support * three cell types not easily distinguished with H&E >> identified by level of nuclei within epithelial layer c. Bowmans glands – serous glands on lamina propria >> allows odiferous molecules to be dissolved on surface 2. histology of the larynx (slide 8) A. lined conducting mucosa except for ridges of stratified squamous covering true vocal cords in some individuals B. cartilage component - contains both hyaline and elastic elements >> become calcified and sometimes replaced with bone as a normal component of aging C. skeletal muscle associated evident >> function in phonation 3. histology of the trachea and bronchi A. pseudostrified epithelium with three other cell types (slide 9) (1) enteroendocrine cells - secrete bioactive amines and peptides into blood vessels of submucosa (2) Clara cells - nonciliated cells with small, tongue-like lumenal projections >> secrete surfactant like substance (slide 10) a. become more numerous in bronchioles 16  (3) goblet cells – secrete mucous on surface B. extremely thick basement membrane C. lamina propria particularly rich in immune macrophages, plasma cells, lymphocytes and mast cells D. submucosa and muscularis mucosa layers now present (slide 11) (1) submucosa not always distringuishable from lamina propria a. extremely rich in glandular epithelia invaginations (2) muscularis mucosa - smooth muscle layer that becomes more prominent in bronchi a. rich network of reticular and elastic fibers E. hyaline cartilage components - provide rigidity of air passageways (1) trachea - C shaped rings connected by smooth muscle (slide 12) (2) bronchi - cartilage plates that become less and less regular (slide 13) 4. bronchioles and terminal bronchioles - distinguished from bronchi via a lack of cartilage (slides 14 and 15) A. lined with conducting mucosa eventually shifting to simple columnar and then simple cuboidal >> occurs over a very short distance (1) Clara cells continue to increase in number distally B. submucosa glands also disappear distally C. terminal bronchiole = smallest exclusively conducting bronchiole respiratory portion - lined with respiratory epithelium >> simple squamous epithelium plus rich underlying capillary network (slide 16) 17  1. histology of respiratory bronchioles >> characterized alternating conducting and respiratory lining A. short passageways (1-4 mm) with three generations of branching B. lined with simple cuboidal epithlium (cilated and nonciliated) C. contain openings to alveolar ducts and individual alveoli 2. alveolar ducts and alveolar sacs A. both are very thin walled structures lined with respiratory epithelium B. alveolar ducts branch 2-3 eventually diverging into alveolar sacs >> 5-6 alveoli clustered off each alveolar sac 3. alveoli - ternimal ends of resiratory passageways A. located off alveolar sacs, alveolar ducts and respiratory bronchioles B. lining composed of two cell types (slide 17) (1) alveolar type I cells - extremely thin simple squamous epithelial cells constituting 96% of lining (2) alveolar type II cells - more rounded cells that constitute 4% of lining >> produce human lung surfactant which decreases suface tension C. very rich capiillary supply (slide 18) (D) alveolar macrophages or dust cells (slide 19) (1) begin as monocytes that exit alveolar capillaries (2) phagocytize particulate debris as they migrate up the "mucociliary esculator” (3) abundant under certain conditions 18  E. alveolar pores - small opening that connect adjacent alveoli >> alternate pathways around obstructions that potentially prevent collapse or overdistension (slide 20) F. interalveolar walls richly enodowed with elastic fibers (slide 21) pleura – lining of the pleural cavities A. reflects from thoracic wall to lungs (slide 22) (1) visceral pleura – outer covering of lungs (2) parietal pleura – internal lining of chest cavities B. histology (slide 23) (1) mesothelium – simple squamous lining a. secrete small amount of serous fluid >> lubricates + allows lungs to slide against thoracic wall b. can be damaged to cause adhesions B. supporting connective tissue rich in collagen and elastic fibers Online slide review: Virtual microscope: http://www.histologyguide.org/slidebox/17-respiratory-system.html Endocrine System On-line reading: http://www.doctorc.net/Labs/Lab24/lab24.htm http://lifesci.dls.rutgers.edu/~babiarz/end.htm introduction to endocrine glands (slide 2) 1. ductless glands that secrete their products (hormones) into the interstitial space of their surrounding connective tissue >> then passes into capillaries (slide 3) A. often associated with finestrated capillaries or sinusoids 2. secretory cells typically arranged as cords or clumps (with a few notable exceptions) 3. cells stain accroding to type of hormone produced 19  A. protein and peptide hormones – cytoplasm stains basophilic to to abundacne of RER (1) occasionally a secretory protein is eosinophilc >> changes staining properties (slide 4) B. steroid hormones – cytoplasm stains eosinophilic due to abundance of SER required for cholesterol synthesis and modification (slide 5) (1) clear vacuoles or “lipid droplets” often seen in cytoplasm pituitary gland or hypophysis - attached to the floor of the brain and often called the master endocrine gland of the body because it exerts control over several other endocrine glands of the body 1. development – portions derived from roof of oral cavity + floor of brain >> epithelial and nervous tissue portions (slides 6 and 7) A. Rathke’s pouch – border between anterior and posterior pituitary 2. relationship to the hypothalamus (slide 8) A. anterior pituitary – portal system with hypothalamus B. posterior pituitary – axons from preventricular and supraoptic nuclei descend into posterior pituitary 3. adenohypophysis >> epithelial portion A. pars distalis - anterior portion (slide 9) (1) histologically arranged as cords and clumps with a rich supply of finestrated capillaries (2) three cell types visible with standard staining procedures (subtypes visible with high specialized staining techniques) a. chromophobes - small, poorly staining cells with indistinct cell boundaries and lacking in cytoplasmic granules 20  b. acidophils - contain darkly staining basic granules i. somatotrophs - produce growth hormone or somatotrophin ii. mammotrophs - produce prolactin (involved in milk production and probably behavioral patterns) c. basophils - contain darkly staining acidic granules i. thyrotrophs - produce thyroid stimulating hormone (TSH) ii. gonadotrophs - produce follicle stimulating hormone (FSH) and leutinizing hormone (LH) iii. corticotrophs - produce adrenocortiotropic hormone (ACTH) B. pars intermedia - posterior portion that is in intimate contact with neural tissue (slide 10) A. contains basophils that synthesize melanocyte stimulating hormone (MSH) >> controls pigmentation of skin plus potentially other not well understood functions C. pars tuberalis - wrapped around infundibulum and composed of neural tissue with a thin wrapping of connective tissue (slide 11) 4. neurohypophysis A. infundibulum - consists of descending axons B. pars nervosa - consists of modified glial cells called pituicytes plus approximately 100,000 axons that have descended from the hypothalamus (slide 12) (1) hormones released – made in hypothalamus and delivered via axons to posterior pituitary a. antidiuretic hormone and oxytoxin 21  5. correlation between neurohypophysis/adenohypophysis and anterior/posterior pituitary (slide 13) A. Rathke’s pouch separates anterior and posterior pituitary B. pars intermedia part of posterior pituitary B. infundibulum + tuberalis not part of anterior nor posterior pituitary thyroid gland - encapsulated mass that wraps around anterior portion of trachea 1. histological and functional unit is the follicle (slide 14) A. follicular cells consist of simple cuboidal epithelium (slide 15) (1) high cuboidal cells >> actively secreting into follicle (2) low cuboidal cells not actively secreting >> sometimes appear almost squamous in shape B. thyroglobulin - large glycoprotein that is binds and stores T3 and T4 (slide 16) (1) phagocytized and processed by follicular cells >> release triioda-tyrosine (T3) and tetraioda-tyrosine (T4) into blood >> increase metabolic rates of several bodily tissues C. both follicular secretion and processing of thyroglobulin controlled by TSH 2. parafollicular cells - located within thin rim of connective tissue underlying follicular cells (slide 17) A. secrete the hormone calcitonin in response to high calcium levels >> stimulates osteoblast activity parathyroid glands – four tiny dark staining masses located on the posterior surface of the thyroid gland (slide 18) 1. thin capsule with trabeculae that incompletely and irregularly divide parenchyma into lobules 22  2. parenchyma (slide 19) A. typical endocrine histology >> cells arranged in cords and clumps with abundant and regularly spaced finestrated capillaries B. cell types (1) chief or principal cells - small, light staining cell with centrally located nucleus >> most abundant cell >> parathyroid hormone (PTH) (2) oxytrophs - larger than chief cells and appear to be full of eosinophilic granules >> mitochondria a. begin to appear just prior to puberty b. typically found grouped together c. unknown function C. increased adipose cells with age >> can accumulate to 50% of gland volume adrenal or suprarenal glands - flattened organs resting on the top of each kidney in man >> functionally and morphologically often considered to be two glands within a single capsule (slide 20) 1. capsule - very thin but surrounded by "adipose capsule" of kidney A. only a few trabeculae >> no hint of lobulation B. delicate sleeves of reticular connective tissue extend inward to provide support for cells of the adrenal cortex 2. adrenal cortex - divided morphologically and functionally into three layers (boundaries not always distinct, particularly in infants), all of which contain steroid secreting cells A. zona glomerulosa - consists primarily of columnar cells arranged in spherical or ovoid groups (slide 21) 23  (1) function = release mineralocorticoids (aldosterone most potent) >> increase sodium and potassium reabsorption in the kidney B. zona fasciculata - consists of slightly basophilic cells arranged in parallel columns which are separated by capillaries (slide 22) (1) cells contain large amount of vesicles >> foamy appearance under LM (2) function = production of glucocorticoids (cortisol most potent) >> several functions involved in the production and mobilization of glucose C. zona reticularis - composed of branching and anastomosing cords of cells surrounded by a mesh of capillaries (slide 23) (1) cells stain more darkly than other zones with smaller, denser nuclei and an accumulation of lipofuscin granules with age (2) function = production of small amounts of sex hormones, primarily androgens >> significance of normal production not understood 3. adrenal medulla - embryonically derived from sympathetic neural tissue >> axons lost and neurotransmitters (hormones) secreted into blood rather than synapse (slide 24) A. large ovoid cells (called chromaffin cells) arranged in tortuous, interwoven cords among intervening connective tissue and capillaries (slide 25) (1) chromaffin reaction – cells that secrete norepinephrine (20%) stain more with chromium salts while cells that secrete epinprine (adrenaline) do not B. function = secretion of catacholamines >> hormonal component of sympathetic response Online slide review: Virtual microscope: http://www.histologyguide.org/slidebox/12-exocrine-glands.html The Eye On-line reading: http://www.doctorc.net/Labs/Lab11/Lab11.htm 24 overview of the eye – trilayered hollow ball that functions to focus light onto the posterior wall and then pass this information on to the brain 1. three tunicas (slide 2) A. tunica fibrosa >> sclera and cornea B. tunica vasculosa >> choroid, ciliary body and iris C. tunica interna >> retina 2. lens (slide 3) 3. anterior and posterior chambers 4. vitreous cavity 5. accessory structures A. conjunctiva B. lacrimal glands C. palpebrae histology of the tunicas of the eye 1. tunica fibrosa – outermost tunic composed of the cornea (anterior 1/6) and the sclera (posterior 5/6) A. cornea – primary focusing medium of the eye >> histology from superficial to deep (slide 4) (1) anterior surface covered by thin nonkeratinized stratified squamous epithelium a. contains many free nerve endings >> painful when damaged b. high rate of cell division >> capable of repair (2) Bowman's membrane – thick basement membrane composed of ground substance and reticular fibers. (3) stroma – core of cornea >> responsible for 90% of thickness. a. many layers of collagen bundles >> fibers parallel in each layer with alternating layers turned 90 degrees 25  b. fibroblasts lie between layers or fibers (4) Descemets membrane – thick atypical basement membrane containing elastin and granulated collagen fibers (5) corneal endothelium – simple squamous epithelium lining the cornea's internal surface B. limbus – the junction between the cornea and sclera (slide 5) C. sclera – opaque fibrous connective tissue that covers the eye's posterior five-sixths >> provides insertion points for the six extraocular muscles that control movement of the eye (slide 6) 2. tunica vasculosa or uvea – middle tunic of the eye composed of three major components >> the choroid (posterior), ciliary body, and iris (anterior) (slide 7) A. choroid – highly vascularized connective tissue layer >> provides blood supply to retinal cells (slide 8) B. ciliary body – ring like triangular thickening at the level of the lens (slides 9 and 10) (1) ciliary processes – irregular epithelium-covered connective tissue outgrowths of the ciliary body extending toward the lens a. act as origins for ligaments of Zinn that insert into of the lens b. lined with a cuboidal epithelium >> stratified (2 layers) in most places i. basal cells highly pigmented >> continuous with pigment cells of retina ii. lumenal cells nonpigmented – produce aqueous humor >> structural filler plus nutritional medium for both anterior and posterior chamber (2) ciliary muscles – groups of smooth muscle bundles near the junction of the ciliary body and sclera >> change the shape of the lens to accommodate for near and far vision (slide 11) 26  C. iris – controls the amount of light reaching the retina and gives the eye its color (slide 12) (1) anterior surface lined with connective tissue >> endothelial cells lost during early childhood (2) stroma consists of highly vascularized connective tissue >> abundant fibroblasts and melanocytes (give color to iris) (3) posterior surface lined with highly pigmented cells (4) muscles of the iris (sldie 13) a. constrictor (sphincter) pupillae – myoepithelial cells just deep to posterior basement membrane >> forms a ring of smooth muscle that contracts under parasympathetic control to partialy close the pupil b. dilator pupillae muscle – smooth muscle whose fibers extend like spokes between the ciliary body and pupil >>contract under sympathetic control to open the pupil. D. canal of Schlemm – located at junction of iris and cornea >> drains excess aqueous humor into venous sinuses (slides 14 and 15) (1) fluid percolates across corneal endothelium plus endothelial lining of canal >> mechanism not understood 3. tunica interna or retina – photosensitive portion of the eye (slides 16 and 17) A. pigmented epithelium – melanin-rich simple cuboidal epithelium (slide 18) (1) pigment functions to absorb photons not absorbed by photoreceptors (2) have apical microvilli (3) Bruch's membrane – elastin rich basement membrane that separates pigmented epithelium from choroid B. neural retina – three layers of cells give rise to nine distinguishable layers (slides 19 and 20) (1) photoreceptors (rods and cones) – composed of a cell body, inner segment and outer segment (slide 21) 27  a. cell body surrounded by Muller cells b. outer segment contains stacks of flat vesicles that contain light sensitive visual pigments i. outer segment cradled in microvilli of pigmented epithelia ii. senescent photoreceptor vesicles phagocytized by pigmented epithelia (2) bipolar cells (along with minor horizontal cells and amacrine cells) – form middle nuclear layer of retinal >> interneurons between photoreceptors and ganglion cells (slides 22 and 23) (3) ganglion cells – unipolar neurons that form innermost layer of nuclei >> axons travel on innermost surface, eventually exiting the eye as the optic nerve C. fovea centralis – conical depression in retina that lies opposite the center of the lens (slide 24) (1) highest concentration of cones >> region with the greatest visual acuity (2) macula lutea – small yellowish disk of fovea visible during ophthalmic inspection D. optic disk – site where the ganglion cells' axons converge exit the eye as the optic nerve (slide 25) (1) site where axons become myelinated (2) no photoreceptors >> anatomical blind spot (3) site where retinal blood vessels enter and leave >> capillaries extend throughout innermost layer except at fovea (4) optic nerve – developed as outgrowth of forebrain >> enveloped by meninges other intraocular structures (slide 26) 1. vitreous body – composed primarily of water and hyaluronic acid A. fibrils around the periphery that form its capsule 28  B. macrophages and fibrocytes sporadically found C. hyloid canal – developmental remnant of the hyloid artery that extended from the optic disk through the vitreous to the lens >> seldom seen in histological section 2. lens – an elastic, biconvex structure that focuses light upon the retina >> nourished by aqueous humor as it is avascular and without a nerve supply A. lens capsule – an elastic and transport basal lamina that covers the entire lens >> prevents penetration by wandering cells (slide 27) B. subcapsular epithelium – varies from low cuboidal to columnar near the equator of lens C. lens fibers – long, narrow, hexagonal, anuclear, specialized epithelial cells that make up the bulk of the lens (1) most fibers stretch across entire anterior/posterior length of lens (2) adjacent cell membranes fused by a variety of plasma membrane specializations including junctional complexes and ridge like processes (3) filled with proteins called crystallins (4) undifferentiated lens fibers remain at equator >> give rise to new fibers throughout lifetime extraocular accessory structures 1. bulbar conjunctiva – covers the exposed part of the sclera (slide 28) A. reflects back to cover the inside of the eye lids >> palpebral conjunctiva B. epithelium varies from stratified squamous to stratified cuboidal, both with abundant goblet cells with underlying connective tissue (slide 29) 2. eyelids or palpebrae (slide 30) A. covered by skin anteriorly and conjunctiva posteriorly B tarsus – dense connective tissue core that provides flexible support and harbors the tarsal glands 29  C. tarsal (Meibomian) glands – modified sebaceous glands >> lubrication D. contain voluntary skeletal muscle E. other glands – produce oily layer which covers tear layer >> retards evaporation (1) glands of Zeiss – sebaceous glands of eyelashes (2) glands of Moll – modified apocrine sweat glands 3. lacrimal gland – tear-secreting compound tubuloalveolar glands located supcrolaterally in the bony orbits (slide 31) A. basophilic secretory acini >> secretes lysozyme in tears Online slide review: Virtual microscope: http://www.histologyguide.org/slidebox/20-organs-of-special-sense.html The Ear On-line reading: http://www.doctorc.net/Labs/Lab11/Lab11.htm structures asscociated with hearing (slide 2) 1. external auditory meatus – tube tranversing from auricle to tympanic membrane (slide 3) A. lined by skin >> lacks dermal papillae B. ceruminous glands – modified apocrine sweat glands that secrete cerumen (ear wax) into hair follicles or directly onto surface C. wall reinforced by elastic cartilage (supericial 1/3) or bone (deep 2/3) 2. tympanic membrane – fibrous membrane that separates external auditory canal from cavity of middle ear (slide 4) A. regions (1) pars flaccida – small non-tense area located superiorly (2) pars tensa – tense region >> firmly attached to the annulus fibrocartilaginous 30  B. layers (1) cuticular layer – consists of thin, hairless skin (2) intermediate fibrous layer – consists of two layers of specialized fibers a. outer layer – fibers arranged radially b. inner layer – fibers arranged in a circular pattern (3) inner mucous layer – simple cuboidal epithelium with thin underlying lamina propria 3. ossicles – endochondrial bone lined with either simple cuboidal or pseudostratified epithelium with a thin underlying lamina propria 4. cochlea – composed of three coiled tubes >> contains the auditory sense organ (slide 5) A. cochlear canal compartments (slide 6) (1) scala vestibuli – originates at oval window and filled with perilymph (2) scala media – separated from scala vestibuli by Reissner’s membrane a. filled with endolymph >> ionic concentration maintained by stria vascularis >> stratified squamous epithelium with highly vascularized lamina propria b. contains organ of Corti (3) scala tympani – separated from scala media by basilar membrane >> filled with perilymph B. spiral ganglion – contains cell bodies of bipolar neurons that give rise to CN VIII (slide 7) C. organ of corti (slide 8) (1) rests on basilar membrane 31  (2) tectorial membrane rest on top of hair cells >> fluid waves depress cilia of hair cells onto tectorial membrane (3) inner and outer hair cells – sensory receptors of the auditory and vesibular systems of the inner ear (slide 9) a. tufted by stereocilia and a single kinocilium b. bending of cilia open mechanical ion channels >> change in membrane potential (4) supporting cells a. pillar cells – provide foundation for tunnel of Corti b. inner and outer phalangeal cells – supportive role to hair cells inner ear structures associated with equilibrium (slide 10) 1. otolith organs – the utricle and saccule (slide 11) A. supporting cells (identified via basal nuclei) surround two subtypes of hair cells (1) goblet cells (Type I) – central layer of nuclei (2) columnar cells (Type II) – supericial most layer nuclei B. cilia embedded within gelatinous glycoprotein layer C. calcium carbonate crystals (otoliths) on top of glyoprotein layer >> move in response to position of head and linear acceleration (1)appear like a rubble field but typically lost when making slide 2. semicircular canals – receptor organ within each canal called the crista ampullaris (slide 12) A. structure similar to otolith organs (slides 13 and 14) (1) hair cells (Types I and II) surrounded by supporting cells 32  (2) cilia embedded within large glycoprotein structure called the cupula B. function – sense organ for rotational acceleration (1) three canals oriented along X, Y and Z planes (2) rotation causes endolymph to reflect cupula in opposite direction >> detected by hair cells Online slide review: Virtual microscope: http://www.histologyguide.org/slidebox/20-organs-of-special-sense.html 33