Final Exam Flashcards
Kidneys
Located retroperitoneally
- *Renal capsule**-surrounds the kidney-fibrous sac
- *Adipose capsule**- contains perirenal fat
- *Renal fascia**- anchors to parietal peritoneum and deep fascia of lumbar muscles.
- *Kidneys**
- Excretion (filter fluids and eliminate from body)
- Regulate volume and blood pressure of blood
- Maintain proper balance of water, salts, acids, and bases
- *Main waste products**
- Urea (from protein breakdown)
- uric acid (nucleic acid breakdown)
- creatinine (breakdown of creatine phosphate in muscles)
Anatomy of Kidney
Cortex
medulla
renal pyramids-striated due to tubules
Papilla- the pyramid’s apex points internally
Renal columns- inward extensions of the renal cortex, separate adjacent pyramids
Lobes- a single medullary pyramid plus the cortical tissue surrounding it.
Hilus – on concave surface
Vessels, ureters, lymphatics and nerves enter and exit
- *Renal pelvis**- flat, funnel-shaped tube, expanded superior part of the ureter
- *Major calices (calyx)**- branching extensions of the renal pelvis. Forms minor calices.
- *Minor calices**- cup shaped tubes that enclose the papillae of the pyramids. Collect urine draining from papillae and empty it into renal pelvis
- *Nephron** (the functional unit of the kidney)
- *Renal corpuscle** (located where it is labeled “cortical nephron”)
- *Glomerulus**
- *Glomerular capsule**
- *Renal (uriniferous) tubule**
- *Proximal Convoluded Tubule**
- *Nephron loop** (“loop of Henle”)
- *Distal Proximal Convoluded Tubule**
- *Collecting duct** (not part of the nephron, but attaches to many nephrons)
FLOW
Note: no segmental vein
Mechanisms of Urine Production
- *Filtration** – filtrate of blood leaves kidney capillaries. Resembles blood plasma but free of cells and lower in protein; “glomerular filtrate”.
- *Reabsorption** – most nutrients, water, and essential ions reclaimed (99% of volume reabsorbed). Occurs throughout renal tubule.
- *Secretion** – active process of removing undesirable molecules from the blood of surrounding capillaries (drugs, antibiotics, toxins, hydrogen ions, etc.)
Renal corpuscle = glomerulus and glomerular capsule
Glomerulus – tuft of capillaries
Capillaries are fenestrated (porus).
Afferent (arise from cortical raiate arteries) and efferent arterioles.
High-resistance vessels. Efferent is narrower than afferent arteriole and so blood pressure is EXTREMELY high in glomerulus.
Glomerular (Bowman’s) capsule-
Parietal layer – simple squamous epithelium
Visceral layer – consists of podocytes- podocytes have pedicels that interdigitate with one another. Filtrate passes into capsular space through filtration slits between pedicels
Filtration Membrane
- *Filtration Membrane- 3 parts**
- Fenestrated endothelium of capillary
- Filtration slits on pedicels of podocytes: each covered by slit diaphragm.
- Intervening basement membrane formed from basal laminae (just protein and carbohydrate sheet) of endothelium and podocyte epithelium
Proximal Convoluted Tubule
Filtrate proceeds to renal tubules from glomerulus
confined to renal cortex.
most active in reabsorption (and secretion as secondary action).
Cuboidal epithelial cells with long microvilli to maximize reabsorbing capacity.
Have many mitochondrial to provide energy.
Loop of Henle
Simple cuboidal to simple squamous to simple cuboidal
- *Thin decending segment**- only permiable to water, reabsorption of water from tubular fluid.
- *Thick ascending limb**- only reabsorption of ions; assists in creation of a concentration gradient in the medulla.
- *Cortical or juxtamedullary nephrons-** depend on length of the loop of henle
note:
-the lower the loop goes: the more concentrated the pee.
Nephrons: 85% corticol-short loop, 15% juxtamed.-long
Distal Convoluted Tubule
- *Distal convoluted tubule** –Simple cuboidal epithelium.
- No microvilli
- Continues as “diluting segment”
- Reabsorption of solutes; water is variable and dependent on hormones (sodium and calcium)
- Part of the juxtaglomerular apparatus-functions in the regulation of blood pressure and is an area of specialized contact between distal convoluted tubule and afferent arteriole
Note: know ADH(Neurohypophisis–> kidneys to uptake water) & Aldosterone (Adrenal cortex-kidneys to uptake salt)
Juxtaglomerular Apparatus
- *Juxtaglomerular cells** in afferent arteriole– detect falling blood pressure, and secrete renin in response
- *Macula densa** – portion of distal convoluted tubule
- Tall, closely packed epithelial cells
- Act as chemoreceptors – sense when solute concentrations fall below critical level. Signal juxtaglomular cells to secrete renin (targets the renal cortex to secrete aldosterone which makes the kidneys reabsorb salt and thus water bringing up blood voume and pressure)
Note: Dieretics target the DCT to prevent the uptaking of sodium, and thus water.
Collecting Tubules (Collecting ducts)
- Collecting tubules – receive urine from distal convoluted tubules.
- Run from cortex into the deep medulla. Adjacent collecting tubules form larger papillary ducts that empty into minor calices through the renal papillae.
- Made of simple cuboidal epithelium which thickens to form simple columnar papillary ducts.
Urinary Bladder
3 layers:
Mucosa with distensible transitional epithelium and lamina propria
-Thick muscular layer (detrusor muscle)- smooth muscle fibers arranged in inner and outer longitudinal layers and a middle circular layer.
-Fibrous adventitia (superior surface is parietal peritoneum).
-Trigone
-Prostate gland
Urethra
-Transitional to stratified squamous (in to out)
-Internal urethral sphincter –involuntary smooth muscle that keeps urethra closed in between voidings
-External urethral sphincter (voluntary control)
In females –opens to external urethral orifice just anterior to vaginal opening and posterior to clitoris.
In males – three named regions
-Prostatic urethra – passes through the prostate gland
-Membranous urethra – through the urogenital diaphragm
-Spongy (penile) urethra – passes through the length of the penis and opens at external urethral orifice.
Carries both semen and urine (not simultaneously)
Digestive System
Organs are divided into two groups:
The alimentary canal
Mouth, pharynx, and esophagus
Stomach, small intestine, and large intestine (colon)
Rectum and anal canal
Accessory digestive organs (not part of the tube)
Teeth and tongue
Gallbladder, salivary glands, liver, and pancreas
Histology of the Alimentary Canal Wall
- Serosa (in abdominal cavity) vs. adventitia- outside of abdominal cavity loose fibrous connective tissue) vs. both
- Longitudinal muscle (muscularis externa)
- Myenteric (Auerbach’s) nerve plexus
- Circular muscle (muscularis externa)
- Submucosa
- Submucosal (Meissner’s) nerve plexus
- Muscularis mucosae
- lamina propria
- Epithelial lining
Nervous System of Gut
Gut has it’s own nervous system:
Intrinsic -Enteric Nervous System- Submucosal nerve plexus & myenteric nerve plexus
- *Extrinsic**- (ANS) sympathetic (slow down) and parasympathetic (speed up)
- can influence/override Enteric Nervous system
- *Sympathetic**- inhibit muscle contractions (peristalsis) and prevent enzyme secretion
- *Parasympathetic**- opposite (speed up digestion)
Tone= contraction
Extrinsic control from Sympathetic and parasympathetic
Parasympathetic
-Vagus is 75% afferent and 25% efferent
Sympathetic
50/50 afferent and efferent
Peritoneal Cavity and Peritoneum
- *Peritoneum** – a serous membrane
- *-Visceral peritoneum** – surrounds digestive organs
- *-Parietal peritoneum** – lines the body wall
- *Peritoneal cavity** – a slit-like potential space
- *Peritoneal fluid**- a lubricating serous fluid secreted by the peritoneum
- *Mesentery** – a double layer of peritoneum that extends to the digestive system from the body wall
- Holds organs in place
- Sites of fat storage
- Provides a route for circulatory vessels and nerves
Dorsal Mesentary- attaches organ to the posterior wall of the cavity.
Ventral Mesentary- attaches organ to the ventral wall of cavity
Mesenteries
- *Ventral mesenteries**-
- Falciform ligament
- Lesser omentum
- *Dorsal mesenteries**
- Greater omentum (roundabout way)
- Mesentery proper (in the coils between jejunum and ileum)
- Transverse mesocolon from transverse colon
- Sigmoid mesocolon from sigmoid colon
The Mouth and Associated Organs
The mouth – oral cavity
Mucosal layer
Stratified squamous epithelium
Lamina propria (MALT-mucosa associated lymphoid tissue)
The lips and cheeks
Formed from orbicularis oris and buccinator muscles, respectively
- *Uvula**- keeps food out of the nasopharynx
- *Palatoglossal arches** -mark end of oral cavity and the beginning of the oropharynx
- *Palatopharyngeal arches** (in oropharynx)
The Superior Surface of the Tongue
Tongue (stratified squamous)
• Tongue papillae
– Filiform papillae- “rough tongue”(most abundant)
– Fungiform papillae-”mushrooms”(dispersed among filiform p.)
– Circumvallate papillae- v-shaped row
– Sulcus terminalis- border of mouth and pharynx
– Lingual tonsils- big bumps on the back of the tongue
Note: Tastebuds are on papillae
Teeth for Mastication
Permanent dentition- (2I, 2C, 2P, 3M) x4=32
Crown, neck, root
Dentin-bonelike and collagen components, harder than bone covered with enamel on crown and cementum on root
Periodontal ligament-tooth to jaw bone
Gingiva-gum
The Salivary Glands
-Produce saliva; moistens mouth
Water, ions, mucus, enzymes (digestive and anti-bacterial), antibiotics
-Starts digestion of food (enzyme: amylase- breaks down carbohydrates, and only carbohydrates, in the mouth)
–Parotid- only serous cells (water and enzymes)
–Submandibular – serous fliud and mucous
–Sublingual glands- mostly mucous cells
–Parasympathetic (promotes) and sympathetic innervation
The Pharynx
- *Oropharynx and laryngopharynx** – passages for air and food
- *Epiglottis** – protects larynx from food entry
- Lined with stratified squamous epithelium
The stomach
Simple columnar cells: Minimal absorption in stomach, only of alcohol, water, electrolytes, and some drugs (aspirin)
Regions- cardiac region; pyloric region; fundus; body
Characteristics- greater and lesser curvatures; rugae
Muscularis externa- 3 layers (additional oblique layer)
Pyloric region (in order):
Pyloric antrum
Pyloric canal
Pylorus (opening)
Pyloric sphincter (gastroduodenal sphincter)
Note: from stomach until anus it’s Simple columnar cells (secretion and absorption)
Note: After you swallow, food is considered a Bollus, and after it’s liquified in the stomach, it’s called chyme
Short-term storage reservoir
Secretions:
intrinsic factor
Pepsinogen
HCl
Gastrin
mucus
Two types of tubular glands
Chemical and enzymatic digestion is initiated, particularly of proteins
Liquefaction of food
Slowly released into the small intestine for further processing (1.5L/3 hours)
Gastric glands(of Gastric pits)- 3 types of cells
- *Mucous Neck cell** (goblet)- release mucus to protect mucosa wall from acid and pepsin
- *Parietal cells**- HCl and intrinsic factor (allow B12 absorption by small intestine).
- *Chief** cells- numerous and release pepsinogen, and with HCl to pepsin(breaks proteins down to amino acids)
2 cell types of Pyloric gland
- *G-cells** - release gastrin (hormone) which targets cells in the stomach to secrete, which promote digestion.
- *Enteroendocrine cells** - stimulates parietal cells to secrete acid and increases pyloric contraction; relaxes pyloric sphincter
- *Mucous neck cells** (cardiac & pyloric regions)
- to release mucus
If we can eat tripe, why don’t we digest our own stomach?
- *Mucous coat**- alkaline mucus resists the acid and enzymes
- *Tight junctions**-gastric juice can’t seep into lamina propria
- *Epithelial cell replacement**- 3-6 day life span.
The Small Intestine – Gross Anatomy
-Longest portion of the alimentary canal
-Site of most enzymatic digestion and absorption
-Movements: peristalsis; segmentation
Three subdivisions
Duodenum, jejunum, and ileum
Modifications for absorption increase surface area (200 sq. meters!)
Circular folds (plicae circulares)
-Force chyme to spiral and take more time for absorption
Villi – finger-like projections of the mucosa
Covered with simple columnar epithelium
Velvety texture; 1 mm tall; contain lacteals and absorptive cells
Microvilli – apical surface of absorptive cells further increase surface area for absorption and contain digestive enzymes to complete digestion of foods
Intestinal crypts
- *(Lieberkuhn; intestinal glands)** – epithelial cells secrete intestinal juice
- *Paneth cells**- secrete bacteriocide; regulates intestinal flora (vitamin K absorption)
- *Peyer’s patches**- aggregated lymphoid nodules (B-cell clone)
- *Duodenal glands**- (Brunners) bicarbonate mucus (buffer-resist changes to pH)
Intestinal glands of Duodenum
HORMONES:
Secretin to stimulate pancreas to release bicarbonate mucus (buffer)
cholecystokinin to stimulate pancreas to release digestive enzymes, and gallbladder to release bile to breakdown fat
Gastric Inhibitory peptide (GIP)- inhibits gastrin secretion and inhibits stomach emptying into the duodenum.
All are released from the Duodenum when chyme enters it.
Small Intestine- digestive enzymes
Digestion of Carbohydrates begins in the mouth with amylase in saliva. The digestion of proteins begins in the stomach with pepsin. The digestion of fat begins in the small intestine with lipase (and help from bile to emulsify it)
However, the small intestine secretes enzymes that breakdown everything (fat, protein, and carbs)
lipase- breaks down triglycerides into free fatty acids and monoglycerides
Duodenum
-receives digestive enzymes from pancrease, and bile from the liver.
-Brunners’s Glands of the duodenum secrete bicarbonate rich mucus to neutralize stomach acid
-Accessory glands pancreas and gallbladder ducts converge at hepatopancreatic ampulla (sphincter of Oddi) and opens at major duodenal papilla (papilla of Vater)
Main pancreatic duct and common bile duct
The Liver
-bile & cholesterol production; emulsifies fats
>minerals, cholesterol, neutral fats, phospholipids, bile
>bile salts- keep cholesterol dissolved in bile
- Performs many metabolic functions- stores vitamins, processes fats and amino acids, detoxifies from poisons and drugs, makes blood proteins
- Apex lies at level of nipple.
- No peritonium, fused to diaphram
-Porta Hepatis(allenters and exits)
- *Hepatic artery**- right and left, brings blood to liver
- *Right and left hepatic duct**- carry bile, fuse to form common hepatic duct (join gallbladder’s cystic duct to make bile duct)
- *Hepatic portal vein**-right and left- carrying nutrients from stomach and intestines for detox.
Gross anatomy of Liver
Right and left lobe
Falciform ligament(separates lobes)
Quadrate
Caudate lobe
Diaphragmatic end(bare area- no visceral peritoneum)
Porta hepatis- where major vessels and nerves enter/leave
Ligamentum teres (round ligament)- umbilical vein
Ligamentum venosum-ductus venosus
Hepatic vein- empties into inferior vena cava
Microscopic anatomy of Liver
- *Lobule**- size of sesame seed and hexagonal shape (functional unit of liver)
- *Portal triad** (tract)- 3 main vessels
- *-Portal arteriole** (branch of hepatic artery)
- *-Portal venule** (branch of hepatic portal vein)
- *-Bile duct**- is draining bile to the gallbladder.
- *Liver sinusoids**- blood flows from portal venule and out central vein (branches of hepatic veins)
central vein–>hepatic vein–>IVC
The Gallbladder
- Cystic duct joins common hepatic duct to form bile duct and empties into duodenum
- Stores and concentrates bile
- Regulation of contraction from small intestine via enteroendocrine cells secreting cholecystokinin
- Gallstones- too much cholesterol or bile salts can lead to crystallization of cholesterol and can plug cystic duct (Very painful during contraction of cystic duct)
The Large Intestine
- Digested residue contains few nutrients
- Small amount of digestion by bacteria (produce vitamin K-blood clot)
- Main functions – absorb water and electrolytes (500ml to 150ml)
- Mass peristaltic movements force feces toward the rectum a few times a day
Special features of large intestine
- *Cecum**- opening where ileum joins. Contains iliocecal valve to prevent fecal reflux
- *vermiform appendix**- blind tube, tucked up behind cecum, acts like lymphatic organ and destroys pathogens(WBCs)
- *Colon**- ascending, transverse, descending and sigmoid, right colic flexure (hepatic) and left colic flexure (splenic)
- Teniae coli- longitudinal strips of smooth muscle that cause puckering of large intestine
- haustra- the puckered sacs
- epiploic appendages – omental appendices (fat filled pouches of visceral peritoneum)
- *Mucous cells**- line large intestine
Anal Canal
- 3 cm long
- Internal anal sphincter- smooth muscle (involuntary)
- External anal sphincter- skeletal (voluntary)
Male Reproductive System
Sperm route: Testes–> epididymis (maturation) –> ductus/vas deferens –> ejaculatory duct –> urethra –> tip of penis.
Accessory sex glands include seminal vesicles, prostate gland, and bulbourethral glands.
Testes
Testes- produce sex hormones and sperm
Both endocrine and exocrine
tunica vaginalis- serous sac that surrounds each testi
Parietal, cavity, visceral
Tunica albuginea – fibrous connective tissue capsule of the testes
Divides each testis into 250-300 lobules
Lobules contain 1-4 coiled seminiferous tubules – “sperm factories”
Sperm are made in Seminiferous tubules
Travel to the Rete testis
Then to the efferent ductules
Then to the Epididymis: a comma-shaped structure on the outer surface of the testis
Leydig Cells and Sertoli Cells
- *Interstitial cells (Leydig cells)** – respond to LH (from Adenohypophysis) and secrete testosterone and some estrogen –
- Lack of testosterone leads to atrophy of male genitalia
Sustentacular Cells (Sertoli)- respond to FSH and protect the gametes and promote their development.
Gonadotropins- LH (targets testes) & FSH (targets the interstitial cells)
External Male Structures
- *The scrotum** – skin and superficial fascia surrounding the testes.
- Positioning provides an environment 3˚ cooler than body temperature (37º c)
- *Dartos muscle** – layer of smooth muscle in scrotum
- *Cremaster muscle** – bands of skeletal muscle surrounding the testes that extend inferiorly from internal obliques. (balls up and down)
Inguinal canal
- Formed by inguinal ligament (external oblique muscle).
- Canal begins medially at superficial inguinal ring laterally to the deep inguinal ring
- Inguinal hernias- viscera pokes through inguinal canal
Spermatic Cord
- *Cremaster muscle**
- *Lymphatics**
- *Vas deferens**/ductus deferens (same thing)
- *Arterial blood**: testicular arteries
- *Venous blood**: testicular veins that drain the pampiniform plexus.
- *Pampiniform plexus**: surround the testicular arteries and remove heat from arterial blood to keep testes cool.
- *Nerves**: Autonomic nervous system- sympathetic and parasympathetic (control ejaculation and erection respectively) and visceral sensory nerves
Ductus Deferens & Urethra
Ductus deferens joins with the seminal vesicle to form the ejaculatory duct.
Ejaculatory duct runs within the prostate gland to empty into prostatic urethra
Lined with:
-Inner mucosa- pseudostratified ciliated columnar
-Muscularis: smooth muscle that creates peristaltic waves to propel sperm
-Outer adventitia
The Urethra
-Carries sperm from the ejaculatory ducts to outside of body or urine from bladder to outside of body
Three parts:
-Prostatic urethra in prostate
-Membranous urethra
-Spongy (penile) urethra in penis
Accessory Glands-produce bulk of the semen
The seminal vesicles (glands)
-joins the ductus deferens to form ejaculatory duct within prostate gland
-Secretes about 60% of the volume of semen
Fluid contains:
-Fructose to nourish sperm
-Other substances to enhance fertilization (prostaglandins, immune suppressants, sperm mobility enhancers, enzymes for sperm clotting)
- *The prostate gland**-size of a chestnut
- Encircles the prostatic urethra
- Secretes about 25-30% of seminal fluid
- Contains substances that enhance sperm motility and clot and liquefy ejaculated semen
random: when they test for prostate cancer they test for: PSA= Prostate specific antigen
- *The bulbourethral glands**
- Pea-sized glands inferior to the prostate gland
- Produce a mucus
- Mucus enters spongy urethra prior to ejaculation
- Cleanses urethra and enhances pH for fertilizations
The Penis
- Arteries and nerves lie near dorsal midline
- Sensory dorsal nerves
- Dorsal arteries
- Dorsal veins
- Deep artery- runs within each corpus cavernosum.
Erectile bodies:
-Corpus spongiosum- midventral body (around urethra)
-Corpora cavernosa: make up most of mass of penis (top two).
Anatomical references to the penis are when it’s erect
The Ovaries
- Small, almond-shaped organs
- Held in place by ovarian ligament and suspensory ligament and mesenteries
- Ovarian arteries – arterial supply
- Innervation from parasympathetic and sympathetic branches
- *Tunica albuginea**- fibrous capsule
- *Ovarian cortex**- houses the developing oocytes
- *Ovarian medulla**- loose connective tissue containing the largest blood vessels, nerves, and lymph vessels of the ovary.
- *Hilus**- where blood vessels, nerves, lymph vessels exit/enter.
- *Follicles**- sac-like structures that enlarge as they mature and release oocyte
The Ovarian Cycle:
Occurs in three phases:
- *Follicular phase**- follicles grow and develop under influence of FSH. LH causes follicles to create hormones (estrogen). 14 days
- *Ovulation**- one oocyte exits after surge of LH from anterior pituitary gland, swept by fimbriae into uterine tube
- *Luteal phase**- corpus luteum, part of follicle that remained in ovary. It secretes estrogens and progesterones to prepare uterus for pregnancy. If no pregnancy- it becomes a scar called corpus albicans
Players in Ovarian cycle
- *Primordial follicle** (primary oocyte) -1,000s
- *Primary follicle**
- Granulosa cells-epithelial follicular cells
- Theca follicili- connective tissue around follicle
- Zona pellucida- protein coat around oocyte that sperm must penetrate.
- *Secondary follicle**
- Antrum-fluid filled cavity
- Corona radiata- granulosa cells surrounding oocyte
- *Graffian follicle**- mature follicle
- surge of LH triggers release of Graffian follicle
- *-Corpus luteum-** remnants of Graffian follicle after ovulation
- becomes an endocrine gland-secretes estrogen and progesterone to prepare the uterus for fertilized egg. If no fertilization takes place, it becomes a scar called Corpus Albicans, which no longer secretes progesterone, and thus triggers menstration.
Hormonal Regulation: Ovarian Cycle
&
Gametogenesis: Oogenesis/ Female Meiosis
Hormonal Regulation: Ovarian Cycle
FSH targets granulosa cells
LH targets the thecal cells to secrete androgens (generic sex hormones which are converted into estrogen by the granulosa cells while under the influence of FSH.
Gametogenesis: Oogenesis/ Female Meiosis
- Takes many years to complete
- Oogonia- stem cells
- Primary oocyte- arrested in early stage of meiosis I. Only when ovulated do they complete meiosis I
- Secondary oocyte- arrested in meiosis II until fertilization
- Ovum (mature oocyte) does not occur until meiosis is finished when fertilization occurs!
- Polar bodies- degenerate without being fertilized. Discarded daughter cells.
The Uterus
- *Fallopian tubes/oviducts**
- *Infundibulum**- lateral opening, funnel shape.
- *Fimbriae**- sweep the oocyte into the uterine tube through infundibulum
- *Ampulla**- site of fertilization
- *Isthmus**- medial third of uterine tube.
- Simple ciliated columnar
The Uterus
- Normally anteverted (can be retroverted)
- Body
- Fundus- region superior to entrance of uterine tubes
- Isthmus- narrowed region near cervix
- Cervix- fibrous ring that keeps uterus closed
- Cervical canal
- External os
- Internal os
Uterine Wall-3 Layers
- *Perimetrium**- visceral peritoneum
- *Myometrium**- smooth muscle for contractions
- *Endometrium**- internal mucosal lining, consists of simple columnar epithelium
- *Stratum functionalis**- shed during menstruation
- *Stratum basalis**- forms new functional layer after menstruation
Ligaments and pouches of the uterus
- *Broad ligament**
- *Suspensory Ligament-** ovarian blood vessels and nerve
Vesicouterine pouch-between uterus and bladderRectouterine pouch-between uterus and rectum
The Vagina
Consists of three coats
Adventitia – outter most layer
Muscularis – smooth muscle
Mucosa – marked by transverse folds (rugae)
stratified squamous epithelium
Vaginal orifice
Fornix – recess formed at the superior part of the vagina, posterior is largest, anterior and lateral
The External Genitalia - vulva/pudendum
- *Mons pubis**- fatty, rounded pad overlying the pubic symphysis
- *Labia majora**- female homologue to scrotum and extend posteriorly from mons pubis
- *Labia minora-** enclose vestibule
- *Vestibule**- houses the external openings of the urethra and vagina
- *Clitoris-** homologous to penis, has glans and a body
- Corpora cavernosa
Week 1: from Zygote to Blastocyst
Oocyte is fertilized in the uterine tube (ampulla) and the zygote (fused nuclei) travels to the uterus.
Cleavage (by mitosis)
Morula
-12-16 cells
-72 hours after conception
-Reaches uterus (day 4)
Blastocyst is formed (day 4-7)
-100 cells large with a central, fluid filled cavity (blastocoel) inner cell mass (becomes embryo) and trophoblast (becomes placenta)
-Day 6 blastocyst implants into uterus (6-11 days)
Embryonic stage- Week 2
-Occurs during implantation
-Inner cell mass divides into two sheets of cells
-Epiblast-amniotic sac (holds amniotic fluid)
-Hypoblast-yolk sac (forms digestive tube and blood cells)
Both form two fluid filled sacs (think two balloons together)
2sheets of cells make up the bilaminar disc -gives rise to whole body
Week 3- Gastrulation (starts d14-15)
- Epiblast cells proliferate and swell up
- Epiblast cells migrate into primitive streak
- Endoderm
- Mesoderm
- Ectoderm
- Once three layers are in place, now embryo status
Notochord
- End of primitive streak is a swelling called the primitive node.
- Epiblast cells are invaginating here migrate anteriorly with some underlying endoderm.
- They form the notochord
- Defines the body axis
- Appears day 16 and at day 18 it has reached the head region
Neurulation
- Notochord signals overlying ectoderm to form spinal cord and brain
- Ectoderm thickens into a neural plate
- Neural plate folds inward as a neural groove
- Groove deepens to pinch off- neural tube
- Closure of neural tube begins at end of week 3, starts at neck and spreads caudally and cranially (neural tube defects- triple screen during pregnancy)
- Closure complete at end of week 4.
- Neural crest cells are pulled into body with invaginating neural tube. Ectodermal in origin and form sensory nerve cells.
Neural tube begins forming at end of week 3 (head and tail), if neural tube doesn’t close properly there are birth defects like Spinal bifita
Mesoderm begins to Differentiate
Middle of week 3 mesoderm differentiates into 3 types:
Somites- mesoderm closest to notochord forms paraxial mesoderm.
Coelom cavity forms serous cavities of ventral body cavity- peritoneal, pericardial, and pleural cavities.
