Human Anatomy Exam 5

Endocrine, Digestive, Urinary, and Reproductive Systems

Endocrine gland (general)

“ductless” glands that secrete chemical messengers (hormones) directly into extracellular fluid, which is then transported to the bloodstream.

Exocrine gland (general)

Glands that have a duct formed by invagination which produces a tube with a gland at its base. Secretory products are released into the duct and are often not regulatory in nature.

Hormone

Products of endocrine glands that are regulatory and carried by the blood.

Neural Transmission

Cell-to-cell communication at a synapse.

Neurotransmitter transmits a message across a synaptic cleft by simple diffusion, binds to receptors on the postsynaptic membrane, which triggers postsynaptic cell to produce a response.

Endocrine Hormone Transmission

A molecule transmits a message (carried by the blood) from an endocrine tissue to a “target cell”.

1. Epithelial Endocrine Tissues — derived from epithelial tissue

2. Neural Endocrine Tissue — derived from neural tissue (hormones often called neurohormones)

Pituitary Gland (Hypophysis) + its 3 distinct parts

Endocrine gland that sits on the sella turcica and is connected to the hypothalamus by the infundibular stalk. Often referred to as the “master gland”, though this is inaccurate as the hypothalamus controls the pituitary.

Parts:

1. anterior pituitary

2. intermediate pituitary

3. posterior pituitary

Anterior Pituitary Glands (tissue derivation + hormones)

Embryonically derived from the epithelial tissues over the roof of the mouth, true glandular tissue. Secretes six hormones:

1. Thyroid Stimulating Hormone (TSH): stimulates thyroid secretion and growth

2. AdrenoCorticoTropic Hormone (ACTH): stimulates adrenal cortex to secrete glucocorticoids

3. Growth Hormones (GH): stimulates growth (all cells)

4. Follicle Stimulating Hormone (FSH): stimulates follicular development (in gonads)

5. Luteinizing Hormone (LH): stimulates ovulation

6. Prolactin (PRL): stimulates milk production

Intermediate Pituitary Gland

Small structure of the pituitary that secretes melanocyte stimulating hormone (MSH). Plays an insignificant role in humans, stimulating melanin production from melanocytes

Posterior Pituitary Gland (tissue derivation + hormones)

Pituitary portion derived from neural ectoderm, not a true glandular tissue. Neurons originate from the hypothalamus and extend through the infundibulum to synapse on the pituitary capillary network.

Secretes two hormones:

1. AntiDiuretic Hormone (ADH): acts on the nephron of the kidney to increase water retention (less peeing), causes vasoconstriction of blood vessels

2. Oxytocin: acts on smooth muscle causing contraction, particularly with uterus and mammary glands

Hypothalamus (endocrine)

Secretes multiple regulatory hormones that control the secretion of the six anterior pituitary hormones, detects changes and regulates the level of other hormones.

Pineal Gland

In posterior roof of the third ventricle, light sensitive gland that produces melatonin at night and is important to circadian rhythm

Thyroid Gland

Endocrine gland right below the larynx composed of two lobes with a central connecting isthmus. Responsible for secreting two classes of hormones:

1. Thyroid Hormones (T3, triiodothyronine and T4, thyroxine)

2. Calcitonin

Follicular Cells (thyroid)

Cells that form the walls of the follicles and secrete the thyroid hormones thyroxine (T4) and triiodothyronine (T3), which increase metabolic rates of all cells

C Cells (Thyroid)

Cells located between the follicles of the thyroid gland, secrete calcitonin which decreases the amount of calcium in the blood (increases calcium absorption of the bones)

Parathyroid Glands

Tiny glands that lie on the posterior surface of the thyroid gland. Secrete parathyroid hormone (PTH) which stimulates bone to release calcium (increases calcium levels in the blood)

Thymus Gland

Endocrine gland located behind the sternum within the mediastinum, important during development as it stimulates the development of the immune system (white blood cell production)

Pancreas (endocrine function)

Lies below the stomach, endocrine cells of the pancreas are the pancreatic islets, which are composed of two major cells types:

1. alpha cells — secrete glucagon (release stored glucose into the blood)

2. beta cells — secrete insulin (store glucose, allow cells to absorb glucose)

3. delta cells (small proportion) — secrete somatostatin (inhibits insulin and glucagon secretion)

Adrenal Glands

Endocrine glands that lie on top of the kidneys and are composed of two distinct regions: inner medulla and an outer cortex

Adrenal Cortex

Thicker layer of the adrenal glands, surrounds the adrenal medulla. Three zones:

1. zona glomerulosa — outermost layer of the cortex, secretory hormones regulate ion levels

2. zona fasciculata — middle layer, secretes glucocorticoids (cortisol, etc)

3. zona reticularis — innermost layer, secrete androgens in minute quantities

Adrenal Medulla

Embryological nervous tissue, functions as part of the sympathetic nervous system to release catecholamines (epinephrine and norepinephrine)

Testis (endocrine)

Play a dual role in producing sperm (gametes) and sex hormones. Major sex hormone produced is testosterone, which stimulates development of the male sex organs, as well as secondary sexual characteristics. Interstitial cells of Leydig produce testosterone

Ovaries

Dual function in producing gametes and sex hormones, estrogen and progesterone. Hormones are involved in development of the development of female sex organs and secondary structures, as well as the regulation of the menstrual cycle. Estrogen is produced in the follicular cells of the follicle. Progesterone (major hormone in pregnancy) is produced in the corpus luteum.

Additional Endocrine Tissues (brief list)

1. Heart — cells in atria produce Atrial Natriuretic Hormone (ANH), increases fluid loss at the kidney

2. Kidney — specialized cells secrete erythropoietin when oxygen levels begin to drop, stimulates red blood marrow to increase red blood cell production. Also secretes renin from the juxtaglomerular apparatus, which converts to its active form (angiotensin) to stimulate the adrenal cortex to secrete aldosterone

3. The GI Tract — produces and secretes many different hormones into the GI Tract, regulates activity in different areas to increase coordination

Parietal peritoneum

Division of the peritoneum that is not in contact with the organs, instead lines the abdominopelvic cavity.

Visceral peritoneum

Division of the peritoneum that surrounds and covers the abdominal organs

Mesentery

Portions of the peritoneum that do not enclose any organ and instead form a double fold (visceral and parietal meet) in which blood vessels, nerves can travel and the organ is suspended through

Perioneal Cavity

Cavity enclosed by the parietal peritoneum anteriorly

Lesser Peritoneal Cavity

Cavity that lies posterior to the stomach and continues within the fold of the greater omentum. Continuous with the peritoneal cavity via the epiploic foramen

Greater Omentum

Double fold of fatty mesentery that lies anteriorly over the small intestines like an apron enclosing the omental bursa. Suspended from the greater curvature of the stomach and transverse colon

Lesser Omentum

Mesentery between the liver and the lesser curvature of the stomach

Falciform Ligament

Mesentery that divides the liver into right and left lobes and secures the liver to the diaphragm and anterior abdominal wall.

Mesentery Proper

Mesentery of the small intestine that connects and suspends this organ from the abdominal wall

Mesocolon

Mesentery of the large intestine that connects and suspends the large intestine to the pancreas at the body wall

Broad Ligament

Mesentery of the uterus, partially covers the uterus and attaches it to the walls of the pelvic cavity laterally

Layers of the Alimentary Canal (4, basic list)

1. Mucosa

2. Submucosa

3. Muscularis externa

   1. Longitudinal Layer

   2. Circular Layer

4. Serosa

Mucosa

Innermost layer of the alimentary canal, composed of an epithelial later over a layer of loose connective tissue (lamina propria) and a thin layer of muscle (muscularis mucosa). Epithelial cells are in direct contact with the contents of the GI tract and may be modified for abrasion resistance, secretion, or absorption

Submucosa

A layer of dense connective tissue that houses blood vessels, lymphatic vessels, some glands, and the submucosal plexus

Muscularis Externa

A double layer of smooth muscle that provides the propulsive movements that act upon food in the alimentary canal

1. Longitudinal Layer — outer layer, parallels the long axis on the canal, contraction shortens the tube

2. Circular Layer — inner layer, wraps around the canal, contraction constricts the tube and is thickened in some regions to form sphincters

Serosa

Outermost layer of the alimentary canal, is actually the visceral portion of the peritoneal membrane.

Enteric Nervous System

Two interconnected neural networks that regulate the activity of the gut (myenteric plexus and the submucosal plexus)

Myenteric Plexus

Network of neurons between the two muscular layers that coordinates GI tract movements (peristalsis)

Submucosal Plexus

A network of neurons within the submucosa that is primarily involved in reflex sensation and coordination of secretion.

Oral Cavity

Site of ingestion and initiation of mechanical and chemical digestion. Mastication mechanically digests food by breaking it into smaller pieces. Salivary amylase initiates chemical digestion of carbohydrates and plays a role in cleaning the oral cavity.

Mucosal layer is made up of unkeritanized stratified squamous ET that protects the oral cavity from abrasion.

Tongue (with types of papilla)

Skeletal muscle structure important for manipulating ingested food (for mastication and swallowing). Covered by a mucous membrane and has 3 types of projections:

1. Filiform papilla: most common projection, provides a roughness for gripping ingested food (no taste buds)

2. Fungiform papilla: scattered over the surface of the tongue, associated with taste buds

3. Circumvallate papilla: larges papilla forming a “V” shape over the posterior tongue, associated with taste buds

Teeth

Has a pattern per quarter: 2 incisors, 1 cuspid (canine), 2 premolars (bicuspids), 3 molars (tricuspids)

Enamel: hard tissue that makes up teeth

Dentin: porous mineralized tissue deep to the enamel forming the roots

Pulp Cavity: core of the tooth containing blood vessels and nerves

Salivary Glands of the Oral Cavity

• Parotid: largest salivary gland, located overlying the masseter muscle, drain into the oral cavity via the parotid duct which opens near the second upper molar

• Submandibular: found under mandible, opens into oral cavity via the submandibular duct at the base on the lingual frenulum

• Sublingual: found under the tongue, open to the oral cavity via short ducts (lesser sublingual ducts) along the base of the tongue

Pharynx (+ divisions)

Region where the airways and GI tract come together, divided into:

1. nasopharynx — above the soft palate (airway only)

2. oropharynx — at the back of the mouth (combined pathway)

3. laryngopharynx — at the top of the larynx (combined pathway)

Muscularis externa in this region is skeletal muscle rather than visceral muscle, larynx has unkeritanized stratified squamous ET.

Tonsils in the Oral Cavity

Lymphoid nodules in the oral cavity.

1. Palatine tonsils: located in posterior lateral walls of the oropharynx

2. Pharyngeal tonsils: aka the adenoids, located in the posterior superior wall of the nasopharynx near the opening of the pharyngotympanic tube

3. Lingual tonsils: located in the oropharynx at the posterior base of the tongue

Esophagus

Smooth muscle tube that propels swallowed bolus (food + salivary mucus) towards the stomach using peristalsis. Upper third has skeletal muscle like the pharynx, transitions to visceral muscle by the distal third of the esophagus. Mucosa is protective against abrasion with unkeritanized stratified squamous ET.

Stomach (regions, mucosa, schinters, etc)

Muscular pouch that stores indigested materials while converting it to a fluid consistency (chyme) through continued chemical and mechanical digestion.

Muscularis externa: has 3 layers, the longitudinal and circular layers plus an extra oblique layer, allows for more possible mixing movements.

Sphincters:

• cardiac sphincter: separates esophagus from the stomach

• pyloric sphincter: separates stomach from small intestine (duodenum)

Mucosa: punctuated by microscopic gastric pits folded into rugae that allow for expansion and increase surface area for secretion

Regions:

1. fundus

2. greater and lesser curvatures

3. body

4. pylorus

Gastric pits

Deep pits formed microscopically in the mucosal epithelium. Composed of 4 types of specialized epithelial cells:

1. Mucous secreting cells

2. Parietal cells

3. Chief cells

4. Enteroendocrine cells

Parietal cells of gastric pits

Cells in gastric pits which secrete HCl and intrinsic factor (needed for B12 absorption in intestine). HCl denatures proteins and activates pepsinogen into pepsin for protein digestion.

Chief cells of gastric pits

Produce and secrete pepsinogen, a precursor to pepsin, converted when in contact with HCl (prevents self-digestion)

Enteroendocrine cells of gastric pits

Several different types of cells named for different hormones, important in coordinating activity of the GI tract

Small intestine overview

Major site of chemical digestion and the site for all nutrient absorption. Receives secretory products intestinal mucosa, pancreas, liver, and gall bladder

Folds in submucosa form circumferential ridges called plica circularis. The mucosa, in turn, has intestinal villi that are formed from projections of lamina propria. Villi have microvilli

Plica circularis

Folds in submucosa that form circumferential ridges that allow for increased surface area

What characteristics of the small intestine increase its surface area for absorption and secretion?

Plica circularis, intestinal villi, microvilli all increase surface area

Crypts of Lieberkuhn

Invaginations found between intestinal villi that have epithelial stem cells that divide to produce new ET and push outwards to replace older villi, shed (holocrine secretion) when reacting the ends of villi

Duodenum

First 10-12 inches of the small intestine, receives digestive secretions from the pancreas and liver through ducts along its inner curve. Within the duodenal submucosa are the duodenal glands that assist in neutralizing acidic chyme released from the stomach

Jejunum

Middle 2.5 meters of the small intestine responsible for the final stages of chemical digestion and the majority of nutrient absorption. Plica circularis, villi, and microvilli provide a large surface area for absorption, pronounced in the jejunum.

Ileum

Last segment and the longest part (3.5 meters) of the small intestine that is responsible for absorption of remaining nutrients. Lymphatic tissues, called Peyer’s patches are particularly pronounced in this segment. Joins the large intestine at the cecum, forming the ileocecal valve.

Peyer’s patches

Lymphatic nodes found in ileum tissue that acts in an immune capacity, surveying current contents of the digestive system.

Duodenal glands

Alkaline secreting glands found in the duodenum that aid in neutralizing acidic chyme that enters from the stomach.

Duodenal papilla

papilla where pancreatic and common bile ducts project from the ampulla of Vater and introduce secretions into the duodenum.

Large intestine (overview + divisions)

Last segment of the digestive system that functions to absorb water, minerals, and vitamins. Compacts and stores fecal matter prior to elimination.

Regions: cecum and appendix, ascending, transverse, descending, sigmoid colon, and rectum

Muscularis externa specialization: longitudinal muscle of is localized in three bands (taenia coli), contracts to form pouched called haustra

Pancreas (exocrine function)

Acinar cells (main exocrine cells) function to produce pancreatic juice, which is secreted into the duodenum via the pancreatic duct. Joins the common bile duct at the ampulla of Vater and projects into the duodenum via the duodenal papilla. Sphincter of Oddi regulates the flow of pancreatic juice and bile into the intestine.

Pancreatic exocrine secretions contain bicarbonate that help to neutralize stomach acid in chyme, also is rich in enzymes for digestion of carbohydrates, fats, and proteins

Liver (digestive accessory)

Largest organ in the abdominopelvic cavity, many important functions including the synthesis of bile, stabilization of blood glucose, synthesis of blood proteins, detoxification of blood, etc.

Works in close association with the gall bladder, liver produces and secretes bile, gall bladder stores the produced bile

Ligamentum teres

Thickening of the falciform ligament that is a remnant of the fetal umbilical vein.

Central vein of the liver

Hepatocytes are arranged with these veins at the center, returns processed blood to the circulation via the hepatic vein

Bile canaliculi

Channel for synthesized bile, bile then drains to the gall bladder via the hepatic ducts

Hepatic Blood Flow Pathway

Blood enters the liver via the hepatic artery, delivering oxygen and the fats absorbed from the GI tract. Nutrient rich blood passes between plates of hepatic cells (through sinusoids) and hepatic cells process the blood to remove/metabolize blood contents. Waste materials are then removed from the blood and drained in the form of bile through the hepatic duct. “Clean” blood returns to circulation via the hepatic vein.

Biliary Duct Pathway

Bile drains out of the liver through the right and left hepatic ducts into the common hepatic duct. Common hepatic merges with the cystic duct (leads to/from the gall bladder) to form the common bile duct. Common bile duct merges with the pancreatic duct at the ampulla of Vater.

Sphincter of Oddi is closed between meals, opens when digestion is underway and bile flows from the ampulla of Vater to the duodenal papilla to accelerate fat digestion.

Ampulla of Vater

Small, enlarged space where pancreatic and common bile ducts merge to add their secretions to the duodenum

Sphincter of Oddi

Ring of muscle that can regulate the flow of bile and pancreatic juices into the intestine.

Kidneys

Organs located against the posterior wall, are retroperitoneal (lie behind the peritoneum). Adrenal glands sit on top of these organs. Adipose deposits sit to form a capsule around these organs to provide support and cushioning.

Ureter

Retroperitoneal smooth muscle tube that transports urine via peristalsis from the kidney to the bladder. Lined by transitional epithelium.

Urinary Bladder

Highly elastic smooth muscular sac that is retroperitoneal. Walls of interior bladder had rugae which, along with transitional epithelium, allow the kidney to be highly expandable. Emptying the bladder occurs by contracting the smooth muscle of the bladder wall (the detrusor muscle) and simultaneous opening of the internal and external sphincters of the urethra

Urethra

Thin-walled tube that exits the bladder and is kept closed by the internal (involuntary, smooth muscle) and external sphincters (voluntary, skeletal muscle).

Trigone

Triangular area formed by the entrances of the two ureters and the urethra, makes up the only area of the urinary bladder that is inflexible

Renal Capsule

Tough, fibrous connective tissue tightly adhering to and encapsulating the kidney

Renal Cortex

Outer, evenly colored region of the kidney just under the capsule. Renal corpuscles are found here

Renal Medulla

Inner region of the kidneys that is deep to the cortex and is composed of renal pyramids (8 in a human kidney) separated by renal columns

• Renal pyramids: each pyramid is made up of a collection of collecting ducts that run from the cortex to the apex of the pyramid (the renal papilla). Ducts collectively appear as medullary rays converging on the papilla

• Renal papilla: has tiny openings for the contents of the collecting ducts to drain through, making the area cribosa

• Renal columns: medullary tissue that extends between the pyramids, provides a route for renal vasculature to pass to the cortex

Renal Pelvis

Large, urine filled space formed by the convergence of the minor and major calyces. Exits the kidneys through the hilus to continue as the ureter.

Renal Sinuses

Central cavity of the kidney where the renal calyces and renal pelvis is found, visible as adipose filled spaces between the calyces

Hilus of the Kidney

exit point for urine in the kidney, bridges from the renal pelvis to the ureter

Renal Arteries (blood flow pathway)

1. Renal Artery — enter the kidneys through the hilus, contain wastes and other materials (dirty blood)

2. Segmental Arteries — distribute blood to the lobes of the kidney

3. Interlobar Arteries — branches of segmental that pass between renal pyramids

4. Arcuate Arteries — branches of interlobar that form arches over the top of renal arteries

5. Interlobular Arteries — branches of the arcuate arteries that extend into the renal cortex.

6. Afferent Arterioles — smaller arteries that branch off the interlobular arteries to deliver high pressure blood to the capillaries of the glomerulus

7. Glomerulus — network of high pressure fenestrated (porous) capillaries

8. Efferent Arterioles — drains filtered blood from the glomerulus to the peritubular capillaries

9. Peritubular Capillaries — capillary network around the nephron for reabsorption,

Renal Veins (blood flow pathway)

1. Interlobular Veins — drain blood from the peritubular capillaries out of the cortex to the arcuate veins

2. Arcuate veins — drain blood from the interlobular veins to the interlobal veins

3. Interlobar Veins — drain blood from arcuate veins through the renal columns between pyramids towards the renal pelvis

4. Renal Veins — drain blood out of the kidney to the vena cava

5. Interior vena cava — drain clean blood back to heart

Glomerulus

Network of high pressure capillaries. Blood easily passes though the capillary walls due to its leakiness (porous walls and high pressure) for filtration. Filtered fluid enters the space formed by Bowman’s capsule (renal corpuscle) and travels through the nephron, while the rest of the blood continues to the efferent arteriole

Peritubular Capillary Network

Capillary network formed around the nephron to facilitate reabsorption of materials back to the blood.

Renal Corpuscle

Structure found originating in the renal cortex. Arranged in chains that parallel the interlobular arteries in the cortex. Composed of a small ball of capillaries (glomerulus) enclosed by Bowman’s capsule

Nephron

Functional unit of the kidney. Tube composed of an expanded end (Bowman’s capsule") and the renal tubule proper divided into several segments. Divided into two classifications: cortical and juxtamedullary nephrons

Bowman’s capsule

Double layer of cells that encapsulates the glomerulus forming a cavity that is continuous with the renal tubule

Cortical nephrons

Nephron with renal corpuscles that are located superficially in the cortex, loop of henle rarely extends far in the medulla

Juxtamedullary nephrons

Nephrons whose renal corpuscle is located close to the medulla and whose loop of henle typically extends deep into the medulla

Podocytes

Foot-like extensions that wrap tightly around the glomerular capillaries, part of the visceral epithelium of Bowman’s capsule. Thin slits between podocytes are called slit pores and restrict the size of molecules that can leave the blood and enter Bowman’s capsule

Proximal Convoluted Tubule (PCT)

Highly twisted portion of the renal tubule close to the renal corpuscle, site of the majority of reabsorption. Have microvilli in the walls formed by simple cuboidal ET, to form a larger surface area for reabsorption (reabsorbs glucose, electrolytes, amino acids).

Loop of Henle

Hairpin loop of renal tubule between the PCT and DCT that is lined by simple squamous ET. Divided into descending and ascending limbs. Length of the loop of henle depends on the type of nephron (cortical or juxtamedullary). Uses an osmotic gradient to facilitate osmotic reabsorption of water to the blood.

Distal Convoluted Tubule (DCT)

Twisted portion of the renal tubule far from the renal corpuscle. Drains into the collecting duct. Lacks microvilli on walls formed by simple cuboidal ET, but significant reabsorption occurs here. Point between DCT and afferent arteriole where they make contact forms the juxtaglomerular apparatus.

Collecting Ducts

Larger tubules lined by simple cuboidal ET that gradually transitions into simple columnar ET. Fluid within the collecting ducts drains into the renal pelvis at the renal papillae.

Juxtaglomerular Apparatus

Sensory and regulating structures associated with the glomerulus, formed where the DCT and afferent arterioles cross. Sensitive to changes in blood composition, blood pressure.