Histo 2 (1).pdf

Female reproductive system Function: formation and secretion of hormones. Composed of: 1. Primary sex organs: Two ovaries (mixed gland) which have: a- endocrine function: (secretion of estrogen and progesterone) b- exocrine function: (sec...

Female reproductive system Function: formation and secretion of hormones. Composed of: 1. Primary sex organs: Two ovaries (mixed gland) which have: a- endocrine function: (secretion of estrogen and progesterone) b- exocrine function: (secretion of gametes: oocytes). 2. Secondary sex organs: 1. Two uterine (Fallopian) tubes. 2. Vagina. 3. Uterus. 4. Two mammary glands. 5. External genitalia 1. Ovary: (Paired ovoid organ) The ovary is a mixed gland that secrets hormones and responsible of ovum formation Consist of: A. Stroma: C.T 1. Germinal Epithelium: * Single layer of cuboidal epithelium which transforms to flat cells with increase of age. 2. Tunica Albuginea: Layer of dense white fibrous C.T. located between germinal epithelium and underlying cortex. B. Parenchyma: cortex and medulla. 1. Outer Cortex: * under tunica albuginea, in peripheral portion of the ovary. (The ovary is covered by simple cubic germinal epithelial cells. And is surrounded by a capsule under their epithelial cells called tunica albuginea. The cortex of the ovary contains ovarian follicles). 2. Inner Medulla: in central portion of the ovary. * Highly vascular loose C.T., lymphatics & nerves. OVARIAN FOLLICLES * distributed in stroma of ovarian cortex. * They provide microenvironment for developing oocyte. * Each containing a single oocyte. Types: 1. Primordial follicles 2. Growing follicles 3. Mature (Tertiary) Graafian follicle 4. Atretic follicles. 1. Primordial Follicles: * Located directly under tunica albuginea. * Appear in developing ovaries during 2nd trimester. (This follicle contains primary ova 2N) ❖ From birth till puberty: cortex is occupied only by primordial follicles. ✓ The wall of the primordial follicle is formed by simple squamous follicular cells and basement membrane. In puberty, Secretion of FSH changes the primordial follicle into primary follicle. ✓ Primary follicle is formed by multiple layers of cubic follicular cells called granulosa cells. ✓ Ova is surrounded by thick fibrous layer called zona pellucida. (Zona pellucida: Glycoprotein layer directly surrounding the oocyte) ✓ The granulosa cells start secreting fluid. Then, the primary follicle changes to secondary follicle (growing follicle) under the effect of FSH hormone. 2. Growing follicles: ✓ This follicle contains more layers of granulosa cells and small cavities. The primary ova are surrounded by zona pellucida and corona radiata → (Corona radiata: Single layer of granulosa cells acquiring columnar shape surrounding zona pellucida) ✓ Growing follicles are surrounded from the outer side by two theca layers 1 Theca externa → fibrous C.T, smooth ms cells, (help in the contraction and eventual rupture of the follicle during ovulation) * This layer is more fibrous and less vascularized compared to the theca interna 2 Theca interna → Blood vs, secrete androgens. (Androgens are the precursors of estrogens. These androgens are converted to estrogens by the granulosa cells of the follicle by aromatase enzyme under the effect of FSH.) 3. Mature (Tertiary) Graafian Follicle: ✓ Is the largest follicle which occupies the whole thickness of ovarian cortex and bulges on the surface. ✓ In this follicle ova move to one side of the follicular wall to be connected to the wall by cumulus oophorous (Cumulus oophorous: Group of granulosa cells surrounding corona radiata and separating it from follicular fluid, this structure ensures that the oocyte remains anchored within the follicle as it matures. They facilitate the transport of amino acids, ions, and other molecules necessary for oocyte growth and maturation)  ✓ Primary ova are divided by MI (Meiosis I) to give primary polar body and 2ry ova with (1N) ✓ The primary oocyte is arrested in prophase I of meiosis I from fetal development until puberty. ✓ The primary oocyte completes meiosis I just before ovulation (ovulation: rupture of graafian follicle) ✓ This division is asymmetrical, resulting in two cells of unequal size: A. Secondary Oocyte: This cell receives most of the cytoplasm and becomes the larger cell. (Begins meiosis II but is arrested in metaphase II until fertilization occurs) B. First Polar Body: This smaller cell receives very little cytoplasm and is usually non-functional. ✓ Under the influence of the LH hormone, the mature Graafian follicle in the ovary ruptures, releasing the secondary oocyte into the fallopian tube. ✓ This rupture can cause a small hemorrhage, forming a corpus hemorrhagicum (a temporary structure that forms immediately after ovulation). ✓ The follicle contains theca interna (which produce androgens), and granulosa cells (which convert these androgens to estrogens) Luteinization: After ovulation, the remaining follicle cells (both theca and granulosa cells) undergo luteinization, transforming into luteal cells that form the corpus luteum. The corpus luteum secretes progesterone, which is essential for maintaining the uterine lining for potential pregnancy. If NO fertilization occurs → This follicle become corpus albicans (dense body of C.T). If fertilization occurs → This follicle becomes Corbus luteum under the effect of LH hormone ✓ Collapse of graafian follicle → Cause bleeding forming corpus hemorrhagicum ✓ Primary Oocyte (Diploid): Arrested in prophase I. ✓ Completion of Meiosis I: Forms a secondary oocyte and a first polar body. ✓ Secondary Oocyte (Haploid): Arrested in metaphase II until fertilization. ✓ Completion of Meiosis II (if fertilized): Forms the ovum and a second polar body. M I→ Immature Ova → undergoes M II → Mature ova 1st Polar body 2nd polar body 2. UTERINE (FALLOPIAN) TUBES * Two muscular tubes of great mobility * Responsible for conveying the ova from the ovaries to the uterus. * The site of fertilization. * Have upper ends (free in the abdominal cavity) and lower ends open to (uterine cavity) Parts of fallopian tube: 1. Intramural segment: Short, thick-walled segment which passes through the uterine wall & opens into the uterine cavity. 2. Isthmus: Narrow, short, thick-walled segment. 3. Ampulla: Thin-walled, longest extended segment where fertilization takes place. 4. Infundibulum: Dilated funnel-shaped segment adjacent to the ovary and opens into the peritoneal cavity. It has finger-like extensions = fimbriae. Its wall consists of: 1-Mucosa: * Highly folded * Composed of simple columnar, partially ciliated epithelium on a basement membrane lying on a C.T. lamina propria: a) Ciliated cells: Cilia move ova toward uterine cavity b) Non-ciliated (Peg) cells: Secretory cells producing fluid to provide nutritive material for ovum and helps in capacitation of spermatozoa. 2-Musculosa: * Inner circular and outer longitudinal smooth muscle layers. * Peristalsis plays greater role than cilia in pushing ovum towards uterus. 3-Serosa: Loose C.T. covered with simple squamous mesothelium. 3. UTERUS: * Pear-shaped organ which receives fallopian tubes in its upper part and its lower part opens into vagina. This organ is responsible of implantation and growth of embryo. * Divided into three parts: Fundus, body, and cervix. The fundus and body are histologically similar, while the cervix is different. Fundus → Uppermost, dome shaped part, above entry point of fallopian tube Body → Central part, where implantation of fertilized egg typically occurs Cervix → Lowest, narrow part that connects to the vagina Wall of uterus: 1. endometrium 2. myometrium 3. perimetrium Endometrium: ✓ Consist of simple columnar E.T and lamina propria that contains simple tubular endometrium glands. ✓ lamina propria contains straight and spiral arteries ✓ Both spiral and straight arteries arise from arcuate arteries in myometrium It consists of two layers: 1. functional layer: Forms 80% of endometrium, thick, contain gland in upper part of endometrium, contain spiral artery. This layer shed off monthly, and rapid menstruation (Regenerative part of endometrium) 2. basal layer. Doesn't shed off, contains pair of glands and straight artery (Remains unchanged during menstrual cycle) (Reserve part of endometrium) Myometrium: * Thickest layer of the uterine wall. * Hormone-sensitive: During pregnancy uterus enlarges mainly due to hypertrophy (increase in cell size) with some hyperplasia (increase in cell number) of smooth muscle fibers under control of ovarian hormones especially estrogen. * It returns almost to its original size (involution) within weeks after delivery. * Composed of three poorly-defined layers of smooth muscles: Stratum submucosum: Longitudinal layer of muscles Stratum vasculare: Thickest layer of circular & oblique muscles arranged in 8-shaped figures enclosing large blood vessels Stratum supravasculare: Longitudinal layer of muscles Perimetrium → covers uterus serosa → in fundus and post. Surface fibrosa → in cervix and ant. surface. Menstrual Cycle: * Starts at the age between 12-15 years and continues till age of about 45-50 years. 1. Menstrual (destructive) phase: (from 1st to 5th day) → shedding of function layer 2. Proliferative (follicular-estrogenic) phase: (from 6th to 14th day or 15th days) → regeneration to function layer The following changes occur: → Lumen glands free (narrow lumens and their cells show no secretory function.) → Spiral artery becomes short → Glands become short 3. Secretory (Luteal-pregestational) phase: (from 15th day till onset of next bleeding (~28th)) → in this phase, glands become deep, crowded, and highly tortuous and secrete their secretions. → Spiral artery becomes congested, highly coiled and lengthen to reach surface of endometrium UTERINE CERVIX: *Lower cylindrical part of uterus that protrudes into the vagina. → Internal os → is the junction between cervix and uterine body. → Cervical lumen is narrow, opens into the vaginal cavity at the external os. 1. Mucosa of the cervix: a) The endocervix: The lining of the cervical canal. Formed of mucus-secreting simple columnar cells. b) The ectocervix: External aspect of the cervix that bulges into the lumen of the vagina. Covered by non-keratinized stratified squamous epithelium. * In proliferative phase cervical glands: secretes watery mucin for facilitated movement of sperm * In secretory phase or if pregnancy occurs, under the effect of high progesterone level: Cervical mucus becomes more viscous and scantier thus preventing passage of spermatozoa as well as microorganisms into the body of the uterus. Wall of the cervical canal contains: →Mucosa: simple columnar epithelium tissue →Submucosa: C.T elastic fibers and smooth muscle →Fibrosa 4. VAGINA *Fibromuscular tube, which is capable of marked distension. Connects uterus with extra genitalia. It consists of three layers: mucosa, musculosa and adventitia. Mucosa: Formed of epithelium and lamina propria Epithelium: stratified squamous non-keratinized E.T Lamina propria: This layer forms two folds: Inner fold → forms labia minora Outer fold → forms labia majora Bartholin's gland: Mucus-secreting glands situated on either side of the vestibule. It has a lubricating function. * Great elasticity of vagina allowing its temporary distension during labor is due to abundance of elastic fibers in its lamina propria and adventitia. * Mucus which lubricates the vaginal lumen comes from cervical glands as vagina contains no glands. 5. MAMMARY GLAND: *Pair gland on pectoralis muscle. Modified Apocrine sweat gland Female Breast Development and Structure: * After puberty, female mammary gland enlarges under effect of estrogen due to accumulation of adipose C.T. Branching of duct system= resting (inactive) state. * It remains in this inactive state until pregnancy occurs during which mammary gland assume its full morphologic and functional state= pregnant & lactating state It consists of: Stroma: Interlobular → dense C.T (Between the lobules) Intralobular → loose C.T (Within a lobule) Parenchyma: Resting breast → formed by blind end ducts (blind → because they don’t lead to active milk-producing structures) Pregnant breast → formed by branched ducts with developing alveoli lactating breast → formed by alveoli that open into ducts for milk secretion Parenchyma of breast consist of 15-20 lobes, each lobule in individual gland consists of secretary part → acini lined by simple cubic cell , basement membrane and myoepithelial cells Acini open to: Intralobular duct → lined by simple cubic cells Interlobular duct → lined by simple columnar cells lactiferous duct → lined by double layer of columnar cells lactiferous sinus → under areola  Male Reproductive System Function: Formation of Spermatozoa and Secretion of testosterone hormone Consist of: Testis and two duct systems 1. Primary sex organs: Two testes 2. Secondary sex organs: a- excretory ducts b- Accessory gland ✓ Testis: a- endocrine function (secretion of testosterone) b- exocrine function (production of the male gametes: spermatozoa) Surrounded by 3 Capsules: 1. Tunica Vaginalis → Serous membrane 2. Tunica albuginea → Thick dense C.T Capsule Formed in Posterior mediastinum of testis. From this tunica arise septa that divide testis into lobules. 3. Tunica Vasculosa→ louse C.T. Forms interstitial tissue Contain a. Blood vessels: Fenestrated Capillary. b. interstitial Cell: myoepithelial cell. c. Leydig cells: Forms endocrine part. * Parenchyma of testis Consist of tubule that divides into 1. Intratesticular tubules: →Contain Seminiferous tubules, tubuli recti and tubuli retti or rete testis 2. Extratesticular tubules: → Contain Vasa efferentia, epididymis, Vas deferens and ejaculatory duct. Seminiferous tubule: U-shape tubule lined by 2 types of cells. These two cells rest on basement membrane: 1.Spermatogonia 2. Sertoli cell. ✓ Spermatogonia: divide by mitosis and give two types of spermatogonia A, B A type →Stem cells For B and itself. B type →Divide by mitosis and give large cells called "Primary Spermatocyte" → Spermatozoa is formed by two processes: 1. Spermatocytogenesis→ Formation of spermatid from primary spermatocyte 2. Spermiogenesis→ Differentiation of spermatid to form spermatozoa ✓ Primary Spermatocyte divides by M1 to give small cell called secondary spermatocyte with 1N. ✓ Secondary spermatocyte divides by M2 to give (4) Spermatid in the center of tubules. The process of spermiogenesis to Form motile Spermatozoa occurs by the Following changes: 1. Golgi complex forms Acrosome Cup Vesicle filled by lytic enzymes. 2. Centriole forms flagella → Tail of sperm. 3. Shrinking of the body of Spermatid * Sertoli Cells: Columnar Cells Contain lateral pockets and forms basal pelt which divides the lumen into basal part that contains spermatogonia and luminal part that contains spermatocyte *Functions of Sertoli cells: 1. Protection of sperms. 2. Trophic to sperms 3. Fermentation of testicular barrier. 4. Secretion of androgens, ABP to activate spermatogenesis, secretion of Anti-Mullerian factors *Seminiferous tubule empty to "tubuli recti"→ short straight part of seminiferous which is lined by simple cubic C.T, basement membrane and myoepithelial Cells. The seminiferous tubule opens to → tubuli recti (simple cuboidal cell partially ciliated) → to Vasa efferentia (lined by columnar cells with stereocilia) → to epididymis (long convoluted tubule lies along the outer side of testis) (pseudostratified columnar ciliated C.T) Function of epididymis→ Storage of spermatids (opens to Vas deference) * Vas deference: Conducts Semin to ejaculatory duct: * Ejaculatory duct: Consists of: →Mucosa: pseudo-stratified columnar and lamina propria →Musculosa: Smooth muscle cells, circular and longitudinal →Fibrosa: C.T * Prostate: Collection of tubulo-alveolar glands under the lower pole of the Urinary Bladder. Secrets milky-like fluid rich of acidic phosphatase and citric acid. Structure 1. Fibromuscular stroma: C.T Fiber, cells, Smooth muscle Contracting during ejaculation. 2. Parenchyma: E.T Forms secretary part and duct. Prostate Contains 3 Parts: 1. mucosal→Small part in the mucus of the urethra. 2. Submucosal→medium sized part. 3. Fibrosa→ Large part Secretory unit is lined by pseudo-stratified columnar ciliated C.T. The lumen contains small stones. * Duct of the gland is lined by: Simple Cuboidal E.T, the ducts change to transitional in the terminals of it. * Seminal vesicles: Pair of glands attached to the lower aspect of the urinary bladder, secret yellow fluid rich in fructose and protein for sperm nutrition. Its alkaline fluid helps in naturalization the acidic environment of the vagina Structure of the seminal vesicles: Mucosa→ highly folded and lined by of pseudo stratified columnar ciliated E.T. Forms secretary part of the vesicle and duct. Each seminal vesicle joins with vas deference to form the ejaculatory duct which opens then to the prostatic urethra. Musculosa→ Smooth cell, contraction leads to proper secretion to urethra. Fibrosa→ loose.C.T * Bulbourethral gland: Compound tubulo-acinar gland, lined by simple columnar E.T, secrets mucous fluid For clearing the urethra  Special Senses: General senses: 1. Exteroceptive 2. Interoceptive 3. Proprioceptive (muscles and joints) *Free nerve endings surrounded by C. T capsule Special Senses: 1. Vision (Sight)(Eye) 2. Hearing 3. Taste 4. Smell ➔ Photoreceptor System (Eye): It consists of the eye and supporting organs. The Eye consists of 3 layers: 1. Fibrosa → Outer layer divided into: A. Cornea → 1/6 of the anterior surface B. Sclera → 5/6 of the anterior surface, Maintain the shape and protect the Eye 2. Vasculosa → Divided into 3 parts: A. Choroid B. Ciliary body C. Iris 3. Nervous layer → Retina 1. Tunica Fibrosa: the outer layer and divided into: A. Cornea: is transparent, avascular, colorless membrane covers the anterior 1/6 of the eye ball and arranged into 5 layers as follows: 1. outer epithelial layer: forms stratified squamous C.T 2. bowman's membrane: thick C.T forms basement membrane for the outer C.T 3. corneal stroma: thick C.T contains of collagen fibers and fibroblast cells 4. Descemet's membrane: forms basement membrane for the inner C.T 5. inner epithelial layer: forms simple cuboidal endothelial cells B. Sclera: covers the anterior 5/6 of the eye ball. Maintain the shape and protect the eye and sites of muscular attachment and consist of: 1. Episclera: loose C.T layer, highly vascular and innervated 2. Stroma: dense C.T layer contain irregular collagen fibers 2. Tunica Vasculosa: is divided to 3 parts: 1. Choroid: vascular part that supports retina and consist of: 1. chorio-vascular layer: underneath sclera contains blood vessels 2. chorio-capillary layer: loose C.T contains capillaries and pigmented cells 3. brush border: as a basement membrane for pigmented layer of retina 2. Ciliary body 3. Iris (the pupil in its center) 3. Nervous layer →Retina: contains two layers: A. Pigmented layer: simple cuboidal pigmented cells rest on brush border Functions: 1. secretion of melanin 2. absorption of excess light 3. prevent reflection of light to it 4. phagocytosis to old discs and photoreceptor cells  B. Neural layer: consists of 10 layers: 1. photoreceptor layer: forms by the outer segment cons and rods cells, this segment contain disc filled by iodopsin in cons and rhodopsin in rods. →Discs of rods are separated completely →Discs of cons are incompletely separated Refractive media of the eye: 1. cornea 2. Aqueous humor: Watery fluid fills the anterior and the posterior chambers of the eye, synthesized by the cells that cover the Ciliary body then to the posterior chamber then to the anterior chamber then to Schlemm's canal then to the venous circulation. 3. Lens: biconvex transparent mass surrounded by capsule fixed by zonula ligament Structure: 1. capsule: C.T layer surround it at all 2. Anterior epithelial layer: single layer of cuboidal cells elongated in center, these cells synthesize lens fibers 3. lens stroma: consist of bulk fibers 4. Vitreous body: gel like material fills the eye cavity (vitreous chamber) and give the eye its shape. Accessory organs: 1. Eyelids: are thin hairless folds of skin to protect the eye and keep the cornea clean and moist. Consist of the following: A. Skin: the skin of the eyelids consists of: 1. epidermis: formed by stratified squamous keratinized E.T 2. dermis: thin C.T contains roots of eyelashes hair surrounded by two glands: 1. Moll gland (sweet gland) 2. Zeis gland (sebaceous gland) B. Muscles: are of two groups: 1. orbicularis oculi 2. levator palpibrae C. tarsal plate: dense C.T supporting eyelids contain oil secretory gland, mix with tear for slow movement of tears from the eye D. conjunctiva: thin transparent mucous membrane consists of stratified columnar E.T with goblet cells 2. Lacrimal glands: pair of glands lie in the anterior and lateral aspects eyebrow; this gland consists of: A. Stroma: C.T B. Parenchyma: → Forms duct and acini lined by simple columnar cells, secret tears and watery fluid contain proteins and enzymes → Duct of gland opens into external fornix of eye, these ducts lined by simple cubic cells in the internal angle of eye → Tears enter to the lacrimal canaliculi which open into the lacrimal sac which open into nasolacrimal canal to the inferior nasal meatus. → lacrimal sac and nasolacrimal canal are lined by pseudo stratified columnar E.T → lacrimal canaliculi are lined by simple cubic cells  ➔ Hearing system: Hearing system consists of three ears: 1. External ear: consists of the following: A. pinna: is wave like elastic cartilage covered by thin skin B. lobule: loose C.T and fat C. External auditory canal: 1/3 is a cartilage and 2/3 is bone, lined by skin containing (ceruminous glands) these glands secrets wax for protection * Tympanic membrane: is the membrane that separates the external ear from middle ear, transports the wave of sound to the ossicles and consists of: 1. Outer epithelial layer: epidermis 2. Fibro-elastic layer: supporting the tympanic membrane 3. Inner epithelial layer: simple cubic cells 2. Middle ear: forms the tympanic cavity and filled by air and consists of: A. 3 small bones → 1. malleus 2. Incus 3. stapes B. 2 muscles → 1. tensor tympani 2. tensor stapedius 3. Inner ear: is the bony labyrinths and consists of: 1. vestibule: contain utricle and saccule, lined by simple squamous E.T *Utricle and saccule contain macula. *Macula: is the thickening, lining, and contains a sensory organ for linear acceleration. Consists of: A. Supporting cells B. Hair sensory cells C. Otolithic membrane: gel-like substance contains calcium crystals (otolith) 2. Semicircular canals: Are three canals (anterior, posterior, and lateral) these canals open to the utricle of vestibule by 5 foramens opening contain dilated part is called (ampulla).  *In this ampulla there is crista ampullaris which is a sensory organ of angular movement. Crista ampullaris consists of: A. Supporting cells B. Hair cells C. Capula: gel like without calcium crystals (otolith) *Cochlear canal: bone consist of 2.5 turns contain cochlear duct *Cochlear duct: membranous canal divided by basilar membrane and vestibular membrane to 3 scalae: A. Scala vestibuli: upper B. Scala Media: contain corti organ C. Scala-Tympani: lower Structure of Corti organ: 1. Basilar membrane: C.T and simple squamous E.T 2. Vestibular membrane: consist of two layers of epithelial cells separated by basement membrane: A. Supporting cells: pillary cells, line tunnel B. phalangeal cells: supporting hair cells 3. Hair cells → Outer 3 rows →inner single row 4. Outer wall→ Scala media, highly vascular, stratified E.T *Tectorial membrane: Is a gel like fluid transforms mechanical sound vibrations to sterocilia of hair cells.  CNS Surrounded by 3 meningeal membranes: 1-Dura mater: Thick fibrous layer forms Venus sinuses 2. Arachnoid mater: vascular connective tissue layer separated from pia mater by subarachnoid space fill by CSF 3.Pia mater: thin connective tissue layer contains capillary and adhere to CNS. Spinal cord: It's about 45 cm long pass-through vertebral canal. Upper end connects with medulla oblongata and lower with intervertebral disc of lumber vertebrae. Consist of Grey mater → central part: H in shape. Grey: collection nuclei: soma and nuclei arranged in 10 laminae. 1. Posterior horn → sensory neuron 2. Anterior horn → motor neuron 3. Lateral horn → Only in thoracic and lumber segment of spinal cord 4. Commissural Grey mater → around spinal cord. Six laminae in post horn: 1. Post marginal nuclei → simple touch sensations I 2. Substantia gelantinosa → pain, temperature sensations II 3. Main sensory nuclei → conscious proprioceptive sensation III 4. Substantia reticularis → for sexual sensation IV 5. Clark's nuclei → unconscious proprioceptive sensation V, VI Lateral horn contains nucleus of autonomic system in lamina 7 in thoracic segment → sympathetic. In sacral is parasympathetic.  Anterior horn contains motor nuclei: 1.Venteral motor nuclei (medial and Lateral lX) 2.Dorsal motor nuclei (medial and Lateral VIII) Commissural nuclei in lamina X: 1. Ventral of spinal cord. 2. Dorsal of spinal cord. White mater: collection of myelinated and unmyelinated nerve fibers from tract and fasciculi and relay. → Tract: collection axons that originate from a specific location and terminate at another specific location, carrying out a specific function. → Fasciculi: collection of different tracts contain different origin and function → Relay: synapses between nerve fiber White mater forms 3 columns 1. Posterior column: contain afferent ascending sensory tracts. These are → 1. Gracile tract: arise as axon of a large nerve cell or soma in posterior root ganglion, enter spinal cord and ascend to medulla then relay to gracile nuclei. Axons of this nuclei form internal accurate tract forward to the thalamus and relay in its nuclei. Axons ascend then to cortex nuclei, transport the proprioceptive sensation of the lower half of the body. 2. Cuneate tract: arise from large soma of upper half of posterior root ganglion. Axons of this nuclei enter spinal cord and ascend to medulla relay in cuneate nuclei to form internal arcuate tract → thalamus → cortex. Transport sensations from the upper half of body