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1. Histology- 2 nd slide exam Made with love by AKMAL

2. DISCLAIMER- THIS PPT ONLY COVERS IMPORTANT CONCEPTS. FOR FURTHER INFO YOU GOTTA READ THE TEXT 

3. NERVOUS SYSTEM

4. BASIC INFORMATION-

5. Functional subdivisions of PNS SOMATIC NERVOUS SYSTEM- MOTOR NEURONS TO SKELETAL MUSCLE TISSUE. AUTONOMIC NERVOUS SYSTEM- Sensory neurons from visceral organs to central nervous system . motor neurons to smooth and cardiac muscle glands and blood vessels consist of sympathetic and parasympathetic division. 3. ENTERIC NERVOUS SYSTEM – involuntary sensory and motor neurons controlling gastrointestinal tract . neurons function independently of system and central nervous system

6. Very very important concept (if you don’t know this slide, they’ll probably kick you out) Very important to know this difference

7. Slide 1- spinal cord It has a butterfly shape the Gray matter lies on the inside – Consist of neuron cell bodies . white matter surrounds the Gray matter on the periphery . White matter is composed of myelinated and unmyelinated nerve fibers hence it is white because of the myelin sheath. white matter represents tracts. In the middle exist central canal which is a small canal in the Gray matter which connects the Gray matter of left and right sides .it is lined by ependymal cells. the spinal cord has two grooves that mark its surface – anterior median fissure and posterior medial sulcus

8. Additional info

9. Slide 2- cerebellar cortex the section of cerebellum shows leaf like folic. The cortex is covered by pia mater which appears as a thin layer of collagen fibers . Blood vessels may be seen just beneath the pia mater Outer gray matter is arranged in three layers from outer to inwards: . Molecular layer : Very few nuclei of neurons seen. Many cell processes present. Appears pale Purkinje cell layer : Single layer of big flask-shaped neurons 3. Granular cell layer : Appears very dark because of presence of abundant nuclei of neurons. Inner white matter shows axons Nuclei of neuroglia are present both in gray and white matter.

10. it is important to know the components of these LAYERS REFER PAGE – 234 TO 235 OF TEXTBOOK FOR DETAILED EXPLANATION OF MENTIONED NERUONS OF THE CEREBELLAR CORTEX.

11. SLIDE 3- CEREBRAL CORTEX

12. SLIDE 4 – SPINAL GANGLION Encapsulated by dense connective tissue grouped together on the periphery pseudounipolar neurons with central nucleus surrounded by flattened satellite cells called mantle glial cells between ganglion cells SEPTA of loose connective tissue is present . Afferent fibers are present in the posterior horn and efferent fibers are present in the anterior horn.

13. Cardiovascular system

14. Basic information TUNICS OF BLOOD VESSELS TUNICA INTIMA This layer is lined by  endothelium , which is comprised of  simple squamous  epithelial cells . Just deep to the endothelium are a  basement membrane  and a layer of  subendothelial  connective tissue  that offers support to the overlying cells. 2. Tunica media The middle muscular layer of the blood vessel is the tunica media. The muscle of this layer is  smooth muscle  that is fitted with alpha and beta adrenergic receptors. These receptors are innervated primarily by the  sympathetic nervous system . IN ARTERIES THIS LAYER IS WIDE. NOTE – ARTERIES HAVE MUSCLE + ELASTIC FIBRES HERE BUT VEINS ONLY HAVE MUSCLE FIBRE NO ELASTIC FIBRES. 3. Tunica adventitia/externa The outermost layer of the blood vessels is the tunica adventitia, also known as the tunica externa. This layer is primarily composed of  type I collagen  and  elastic connective tissue  (in arteries). This external layer is responsible for anchoring the vessels to adjacent organs. CONTAINS VASO VASORUM TO SUPPLY VESSELS THEMSELVES FOR TUNICA EXTERNA AND MEDIA. INTIMA ABSORBS NUTRIENTS DIRECTLY FROM THE LUMEN. THIS LAYER IS WIDE IN VEINS.

15. TYPES OF ARTERIES LARGE ELASTIC ARTERIES – AORTA, PULMONARY TRUNK MUSCULAR ARTERIES – MEDIUM OR SMALL Arteries that carry blood to the organs and extremities MIXED ARTERIES are arteries that are located between elastic and muscular arteries example subclavian common carotid common iliac .

16. SLIDE 1- MUSCULAR ARTERY In muscular arteries, the tunica intima is made up of endothelium and internal elastic lamina, which is thrown into wavy folds due to contraction of smooth muscle in the media Tunica media is composed mainly of smooth muscle fibers arranged circularly • Tunica adventitia contains collagen fibres and few elastic fibers .

17. SLIDE 2- VEIN The vein has a thinner wall and a larger lumen than the artery The tunics intima, media, and adventitia can be made out, but they are not sharply demarcated The media is thin and contains a much larger quantity of collagen fibers than arteries. The amount of elastic tissue or of muscle is much less The adventitia is relatively thick and contains considerable amount of elastic and muscle fibers. Note: The luminal surface appears as a dark line, with an occasional nucleus along it.

18. SLIDE 3 – ELASTIC ARTERY Elastic artery is characterized by presence of: Tunica intima consisting of endothelium, subendothelial connective tissue, and internal elastic lamina The first layer of elastic fibers is called the internal elastic lamina. The internal elastic lamina is not distinct from the elastic fibers of media Well developed subendothelial layer in tunica intima Thick tunica media with many elastic fibers and some smooth muscle fibers Tunica adventitia containing collagen fibers with several elastic fibers Vasa vasorum in the tunica adventitia

19. SLIDE 4 – MICROCIRCULATORY BED 4 PARTS- ARTERIOLES, CAPPILARIES, VENULES, ARTERIOVENOUS SHUNTS. Arteriole - small diameter blood vessel that branches out from arteries and leads to capillaries. Their wall consists of endothelial cells, an internal elastic lamina apposed by one or two layers of smooth muscle, and a thin layer of collagen fibers. The inner elastic lamina is usually absent from smaller arterioles. The thickness of vessel wall is usually similar in size to the diameter of the lumen. Venules - small diameter blood vessel that allows blood to return from capillary beds to veins Their wall is composed of an endothelial cell, one or two layers of smooth muscle, and very thin adventitia.

20. HOW TO FIND CAPPILARY- LINE BY LINE RBC IS ARRANGED- DIAMETER OF ONE RBC IS THE THICKNESS OF CAPPILARY. Capillaries are the smallest blood vessels (less than 10 µm in diameter). The thin wall of capillaries is composed of endothelial cells supported by a basement membrane. Three types of capillaries can be distinguished: Continuous capillaries  - continuous endothelium and basement membrane EX- BRAIN, SKIN, MUSCLE, THYMUS Fenestrated capillaries  - endothelial cells contain small, 80 to 100 nm pores called fenestrations (typically with thin diaphragms) EX- KIDNEY, INTESTINE, ENDOCRINE GLANDS Sinusoidal capillaries  - discontinuous endothelium and incomplete basement membrane EX- LIVER, BONE MARROW, SPLEEN

21. SLIDE 5 – ENDOCARDIUM

22. The Purkinje system is a network of specialized muscle cells that carry cardiac impulses to the ventricles of the heart and cause them to contract. Purkinje fibers extend from the atrioventricular (AV) node, divide into left and right branches, and travel beneath the endocardium of the ventricles. Purkinje fibers are modified cardiac muscle cells and stain differently from surrounding muscle cells: Larger cells Large amounts of glycogen Fewer myofibrils Purkinje fibers conduct cardiac impulses faster and more efficiently than normal cardiac muscle cells

23. ENDOCRINE GLANDS

24. important

25. Hypothalmus Contains two nuclei – LARGE CELLED NUCLEI- Contains supraoptic and paraventricular nuclei secrete vasopressin (ADH) and oxytocin . FUNCTION OF ADH- Acts on the tubules of nephron in the kidney and provides the reabsorption of 99 percentage of water from the primary urine increases permeability of nephrons for urea increases blood pressure by promoting the contraction of smooth muscle by causing vasoconstriction in small arteries and arterioles lack of ADH secretion causes diabetes insipidus FUNCTION OF OXYTOCIN- Causes the contraction of the uterine smooth muscles during copulation and delivery causes involution of the uterus after delivery causes the contraction of the myoepithelial cells of the secretary alveoli and alveolar ducts of the breast at the time of breast feeding causes contraction of the myoepithelial cells of the seminiferous tubules of testis at the time of orgasm and ejaculation. Note – these hormones are secreted by hypothalamus but are stored in pars nervosa of posterior pituitary gland in dilated axon terminals called HERING bodies .

26. Small cell nuclei Produce the proteins that promote or inhibit the secretion and excretion of adeno hypophyseal hormones . for example growth hormone releasing factor growth hormone inhibiting factor thyrotropin releasing factor gonadotropin releasing factor etc.

27. HYPOPHYSIS **make a note of these labelings .**

28. How to identify- WE CAN SEE PARS DISTALIS AND INTERMEDIA OF ADENOHYPOPHYIS AND PARS NERVOSA OF NEUROHYPOPHYSIS Histology of cells of pars distalis of Adenohypophysis (anterior pituitary) 1. cells that stain poorly – CHROMOPHOBES Chromophobes represents- Cambial reserves (undifferentiated endocrinocytes ) Partially degranulated acidophiles or basophils old cells and supporting cells 2. Cells that stain well- CHROMOPHILS T hey are acidophils and basophils ACIDOPHILS produce SOMATOTROPHS- GROWTH HORMES LACTOTROPHS – PROLACTIN BASOPHILS PRODUCE THYROTROPHS – TSH GONADOTROPHS – FSH and LH ADRENOCORTICOTROPHS- ACTH PARS NERVOSA OF NEUROHYPHOSIS- STORAGE SITE OF HORMONES OF HYPOTHALAMUS VERY IMP – ACIDOPHILS- STAIN PINK/RED BASOPHILES- STAIN BLUE

29. ITS IMPORTANT TO KNOW THE FUNCTION OF THE HORMONES MENTIONED IN THE LAST SLIDE

30. SLIDE 2- THYROID GLAND The thyroid gland is made up of follicles lined by cuboidal epithelium. it can be seen that follicles vary in shape and size Each follicle is filled with a homogenous pink colloid proteinaceous material composed primarily of thyroglobulin that has been produced by the follicular epithelial cells. THRYOGLUBULIN CONTAINS THRYOID HORMONES (T3 AND T4). Parafollicular cells are present in relation to the follicles and also as groups in the connective tissue . THESE CELLS SECRETE CALCITONIN WHICH LOWERS BLOOD CALCIUM LEVELS. In the intervals between the follicles, there is some connective tissue and blood vessels between follicles.

31. QUESTIONS THAT CAN BE ASKED HOW DOES CALCITONIN REGULATE BLOOD CALCIUM LEVELS ? Calcitonin inhibits (blocks) the activity of osteoclasts, which are cells that break down bone Calcitonin can decrease the amount of calcium that your  kidneys  reabsorb and release back into your bloodstream, thus causing lower blood calcium levels. They also increase rate of osteoid calcification.

32. Slide 3- parathyroid gland These glands are made up of masses of cells with numerous capillaries in between Most of the cells (of which only nuclei are seen) are the chief cells which appear as small basophilic cells (purple in color). These cells have a central nucleus. They secrete parathyroid hormone (INCREASE CALCIUM BLOOD LEVELS). Oxyphil cells appear as large as lightly acidophilic with numerous mitochondria. (pink) cells. THESE CELLS ARE A POPULATION OF OLD PRINCIPAL CELLS. THEY INCREASE WITH AGE. Oxyphil cells are few in number Adipose cells are also seen. T he color of oxyphil and ch ie f cells are imp to know

33. SLIDE 4- ADRENAL GLAND The suprarenal gland is made up of a large number of cells arranged in layers. It consists of an outer cortex and an inner medulla • The cortex is divisible into three zones • The zona glomerulosa is most superficial. Here, the cells are arranged in the form of inverted U-shaped structures or acinus-like groups • In the zona fasciculata, the cells are arranged in straight columns (typically two-cell thick). Sinusoids intervene between the columns • The zona reticularis is made up of cords of cells that branch and form a network. • The medulla is made up of groups of cells separated by wide sinusoids. Some sympathetic neurons are also present.

34. Adrenal medulla – predominately under sympathetic control . Contains chromaffin cells- they secrets catecholamines. Dark cells – norepinephrine light cells – epinephrine Adrenal cortex- Zona glomerulosa – secrete aldosterone Function – sodium and water absorption in DCT of kidney. Zona fasciculata- secrete glucocorticoids (cortisol, corticosterone, hydrocortisone) Function – metabolism of carbohydrates, resistance to stress, suppress inflammatory stress and some allergic reactions. Zona reticularis – secretes androgen steroids, to a lesser extend estrogen and progesterone. Imp - The cortex is controlled by ACTH by anterior pituitary which is inturn controlled by CRH by hypothalamus. Important information

35. Lymphoid organs

36. Basic information Primary or central organs site of antigen independent proliferation and differentiation to T&B lymphocytes these are - red bone marrow thymus secondary or peripheral organs site of lymphocyte proliferation and exposure to antigens these are - lymph nodes Spleen MALT - The mucosa-associated lymphoid tissue (MALT), is  a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body Examples include  tonsils, the Peyer patches within the small intestine, and the vermiform appendix .

37. Slide 1 - thymus The thymus is made up of lymphoid tissue arranged in the form of distinct lobules. The presence of this lobulation enables easy distinction of the thymus from all other lymphoid organs The lobules are partially separated from each other by connective tissue septae . Blood vessels enter and leave the thymus by this septa. In each lobule an outer darkly stained cortex (in which t-lymphocytes are densely packed); and an inner lightly stained medulla (in which the cells are diffuse) are present. Medulla contains Epithelial reticular cells and fewer differentiated lymphocytes . Whereas the cortex is confined to one lobule, the medulla is continuous from one lobule to another The medulla contains pink staining rounded masses called the corpuscles of Hassall. They are EOSINOPHILIC and consist of centrally arranged flattened epithelial reticular cells. Their size and number increase with age. Function unknown.

38. Function of thymus Function of stroma of thymus

39. Important blood thymus barrier

40. Slide 2 – lymph node

41. • A thin capsule surrounds the lymph node and sends in trabeculae 3 layers – cortex, para cortex and medulla. • Just beneath the capsule a clear space is seen, This is the subcapsular sinus • A lymph node has an outer cortex and an inner medulla • The cortex is packed with lymphocytes. A number of rounded lymphatic follicles (or nodules) are present. Nodules contain mainly B-LYMPHOCYTES. • Each nodule has a pale staining germinal center surrounded by a zone of densely packed lymphocytes. • Within the medulla the lymphocytes are arranged in the form of anastomosing cords. Several blood vessels can be seen in the medulla. Medulla has 2 components- 1. medullary cords- Contain lymphocytes ,macrophages and plasma cells carried in a loose framework of reticular tissues and fibers . 2. medullary sinuses- join at the hilum delivering the lymph to the M frint lymph vessels of the lymph node .Subcapsular sinus communicates with medullary sinus through trabecular sinuses. • Trabecular sinuses run between lymph nodules Note: All lymphoid tissue are easily recognized due to presence of aggregation of dark staining nuclei . The nuclei belong to lymphocytes.

42. zones of lymphatic nodules – important info forsure will be asked this is the same for spleen.

43. Slide 3- spleen

44. Sense organs

45. Basic info about eye The three tunics from the outside surface of the eye inward are, the fibrous tunic (cornea and sclera), the vascular tunic (iris, ciliary body, and choroid) and (3) the neuroectodermal (nervous) tunic (retina). Fibrous tunic – Sclera- white of eye, dense regular connective tissue. Asvascular . Support and protective function. Cornea- Colorless and transparent. it is avascular. It is the principal light refracting surface. it has pain receptor nerve endings . Vascular tunic - Iris - Together with the pupil, the iris is responsible for  regulating the amount of light that gets into the eye .  The muscular iris moves to shrink the pupil if there is too much light and widen it if there is not enough. The ciliary body - produces the fluid in the eye called aqueous humor . It also contains the ciliary muscle, which changes the shape of the lens when your eyes focus on a near object. This process is called accommodation. The choroid  supplies the outer retina with nutrients, and maintains the temperature and volume of the eye . The choroidal circulation, which accounts for 85% of the total blood flow in the eye, is a high-flow system with relatively low oxygen content. Retina –   The retina contains millions of cells that work together to detect light, turn it into electrical signals and communicate with the brain to produce vision. These tiny photoreceptor cells are called cones and rods.

46. Difference between rods and cones

47. Slide 1 - cornea The cornea is made up of five layers: corneal epithelium, anterior limiting membrane, or Bowman's membrane, corneal stroma, posterior limiting lamina, and endothelium The corneal epithelium is nonkeratinized stratified squamous epithelium The substantia propria is made up of collagen fibers embedded in a ground substance Endothelium is lined by a single layer of flattened or cuboidal cells.

48. More info about layers of cornea

49. Slide 2- posterior wall of eye

50. We can identify 10 layers

51. Slide 3 - Organ of corti Professor will ask to zoom in the organ of corti - this place is where we zoom in.

52. identification We can identify vestibular membrane- 2 layers of squamous epithelium one derived from scala media and one from scala vesitibuli . Spiral ganglion – bipolar sensory neurons. Related to vestibularcochlear nerve. 3. Basilar membrane- separates scala media from scala tympani. 2 zones – zona arcuata and zona pectinate. 4. Stria vascularis – attached to spiral ligament, its an unvascularized epithelium. Responsible for composition of endolymph. 5. Hair cells and supporting cells are present.

53. The end. Good luck. If this helped in any way, let me know 