lecture exam xam 4

hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid glands, thymus, adrenal glands, pancreas, gonads (ovaries/testes)

endocrine system organs

hormones are chemical messengers released by endocrine glands into the bloodstream, they travel through the blood until they reach target cells, where they bind to specific receptors and cause a response

how do hormones work as a signaling system?

hormones = chemical messengers carried in the blood

• endocrine = slower, longer-lasting effects

nervous system = electrical signals through neurons

• nervous = faster, shorter-lasting effects

how is the hormone’s signaling system different from the nervous system’s signaling system?

target cell = has receptors for a specific hormone

• if a cell has the receptor, the hormone can bind and produce an effect

• if a cell does not have the receptor, the hormone has no effect on that cell

what does it mean to be a target of a hormone?

endocrine system regulates long-term body functions by releasing hormones into the bloodstream, hormones help control:

• growth and development

• metabolism (how the body uses energy)

• blood glucose levels

• blood pressure

• calcium balance

• reproduction and sexual development

• stress response

• maintenance of homeostasis

endocrine system’s effects on the body

endocrine system: growth during childhood, regulating metabolism, maintaining blood sugar, puberty

• endocrine = slower, longer-lasting effects

• endocrine controls long-term body regulation

nervous system: pulling your hand away from a hot stove, moving your muscles, sensing pain, changing heart rate immediately

• nervous = faster, short-lived effects

• nervous system controls immediate responses

how do the endocrine system’s effects on the body differ from the nervous system’s?

releases hormones that control the activity of many other endocrine glands, including the thyroid, adrenal glands, and gonads (ovaries and testes)

why is the pituitary gland called the "master gland"?

pituitary is controlled by the hypothalamus, so the hypothalamus is the body's main control center

• hypothalamus

  • detects the body's need for more thyroid hormone

  • releases TRH (thyrotropin-releasing hormone)

• anterior pituitary gland

  • TRH stimulates the pituitary.

  • the pituitary releases TSH (thyroid-stimulating hormone)

• thyroid gland

  • TSH stimulates the thyroid.

  • the thyroid releases T₃ (triiodothyronine) and T₄ (thyroxine)

  • these hormones increase metabolism, growth, and energy use

• negative feedback

  • when enough T₃ and T₄ are in the blood, they signal the hypothalamus and pituitary to stop releasing TRH and TSH.

  • this keeps hormone levels balanced (homeostasis)

control system between the hypothalamus, pituitary gland, and thyroid gland as an example

produces and secretes its own hormones, acts by blood, controlled by releasing and inhibiting hormones from the hypothalamus through the hypophyseal portal system (blood vessels)

anterior pituitary

stores and releases hypothalamic hormones, pathway of nerves, controlled by nerve impulses sent directly from the hypothalamus through axons

posterior pituitary

• GH (growth hormone) – stimulates body growth and protein synthesis

• TSH (thyroid-stimulating hormone) – stimulates the thyroid gland to release T₃ and T₄

• ACTH (adrenocorticotropic hormone) – stimulates the adrenal cortex to release cortisol

• FSH (follicle-stimulating hormone) – stimulates egg and sperm production

• LH (luteinizing hormone) – triggers ovulation in females and testosterone production in males

• prolactin (PRL) – stimulates milk production in the mammary glands

hormones produced by the anterior pituitary gland

• ADH (antidiuretic hormone, vasopressin) – helps the kidneys retain water and increases blood pressure

• oxytocin – stimulates uterine contractions during childbirth and milk ejection during breastfeeding

hormones produced by the posterior pituitary gland

targets kidneys, conserves water, decreases urine production, helps raise blood pressure

antidiuretic hormone (ADH) target cell/organ and response

uterine walls, smooth muscle contracts during childbirth and milk ejection during breastfeeding

oxytocin (OT) target cell/organ and response

thyroid gland, stimulates the thyroid to release T₃ and T₄, increasing metabolism

thyroid-stimulating hormone (TSH) target cell/organ and respone

lactiferous ducts, stimulates lactation after childbirth

prolactin (PRL) target cell/organ and response

adrenal gland, stimulate the release of norepinephrine, epinephrine, and cortisol

adrenocorticotropic hormone (ACTH) target cell/organ and response

skeletal system and skeletal muscles, stimulates growth, repair, and maintenance

growth hormone (GH) target cell/organ and response

ovaries and testes, egg and sperm production

follicle-stimulating hormone (FSH) target cell/organ and response

ovaries and testes, ovulation & testosterone

luteinizing hormone (LH) target cell/organ and response

front of the neck, below the larynx, around the trachea

where is the thyroid gland located in the body?

four small glands on the back of the thyroid

where are the parathyroid glands in the body?

follicular cells (thyrocytes), produce T₃ and T_4, increase metabolism, growth, and development

parafollicular cells (C cells), produce calcitonin, lowers blood calcium levels

what type of cells make up the thyroid and what hormones do they create?

parathyroid hormone (PTH)

what hormone do the parathyroid glands produce?

dissolves bone and increases Ca²⁺

PTH primarily…

located on top of each kidney (one adrenal gland sits on each kidney)

where are the adrenal glands located?

• zona glomerulosa (outermost)

• zona fasciculata (middle)

• zona reticularis (innermost)

layers of the adrenal cortex (superficial → deep)

produces mineralocorticoids (mainly aldosterone), regulates blood pressure and electrolyte (Na⁺ & K⁺) balance by increasing sodium and water reabsorption in the kidneys

zona glomerulosa

glucocorticoids (mainly cortisol), helps the body respond to stress, increases blood glucose, and regulates metabolism

zona fasciculata

gonadocorticoids (androgens), contributes to sexual development and libido; serves as a source of weak sex hormones

zona reticularis

epinephrine and norepinephrine (stress hormones)

adrenal medulla

located deep within the brain, attached to the roof of the third ventricle, lies between the two cerebral hemispheres, near the center of the brain

where is the pineal gland located?

releases melatonin, regulates the sleep-wake (circadian) cycle, released mainly in darkness, promoting sleep, and decreases in light

what hormones does the pineal gland release and what does it regulate?

behind the stomach in the upper abdomen, extends from the curve of the duodenum (first part of the small intestine) on the right side to the spleen on the left side

where is the pancreas located?

alpha (α) cells and beta (β) cells

which cells of the pancreas release hormones?

insulin (beta cells) and glucagon (alpha cells)

what hormones are produced by the pancreas?

raises blood glucose by stimulating the liver to break down glycogen into glucose and release it into the blood

body’s response to glucagon

lowers blood glucose by helping cells take up glucose and stimulating the liver and muscles to store glucose as glycogen

body’s response to insulin

mouth (oral cavity), pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (colon), cecum, rectum, anal canal, anus

digestive tract organs

teeth, tongue, salivary glands, liver, gallbladder, pancreas

digestive tract accessory organs

a double layer of peritoneum (serous membrane) that:

• supports and anchors the digestive organs in the abdominal cavity

• provides a pathway for blood vessels, lymphatic vessels, and nerves to reach the intestines

what is the mesentery?

hangs from the greater curvature of the stomach and drapes over the intestines like an apron, stores fat, cushions organs, helps fight infection, and limits the spread of infection

greater omentum

connects the lesser curvature of the stomach and the duodenum to the liver, supports the stomach and provides a pathway for blood vessels, nerves, and bile ducts

lesser omentum

connects the small intestine (jejunum and ileum) to the posterior abdominal wall, achors the small intestine and carries blood vessels, lymphatics, and nerves

mesentery (proper)

serosa (or adventitia), muscularis externa, submucosa, mucosa

four tunics (layers) of the digestive tract (superficial → deep)

protects the digestive organs and reduces friction (adventitia anchors organs where there is no serosa)

serosa

moves food through the GI tract by peristalsis and segmentation

muscularis externa

supports the mucosa and contains vessels and nerves

submucosa

mucosa

secretion, absorption, and protection

visceral peritoneum (simple squamous epithelium + areolar connective tissue)

structures found in serosa

inner circular smooth muscle, outer longitudinal smooth muscle, myenteric (auerbach) plexus between the muscle layers

structures found in muscularis externa

dense irregular connective tissue, blood vessels, lymphatic vessels, submucosal (meissner) plexus, glands (in some regions)

structures found in submucosa

epithelium, lamina propria (areolar connective tissue), muscularis mucosae (thin smooth muscle)

structures found in mucosa

muscularis externa, contains inner circular smooth muscle and outer longitudinal smooth muscle, these muscle layers contract to move and mix food through the digestive tract

which tunic is responsible for increasing motility?

peristalsis and segmentation

two types of muscular contractions

mixes food with digestive juices and increases absorption

segmentation

propels food forward through the digestive tract

peristalsis

process of breaking food down into smaller molecules that can be absorbed by the body

digestion

movement of digested nutrients, water, and electrolytes from the digestive tract into the blood or lymph, occurs primarily in the small intestine

absorption

movement of food through the digestive tract by smooth muscle contractions

motility

enzymes break large molecules into smaller ones

chemical digestion

physical breakdown, e.g., chewing and stomach churning

mechanical digestion

ingests food, chews it (mechanical digestion), mixes it with saliva, and begins carbohydrate digestion

mouth (oral cavity)

passageway that moves food from the mouth to the esophagus during swallowing

pharynx

transports food to the stomach by peristalsis

esophagus

stores food, mechanically and chemically digests it (especially proteins), and forms chyme

stomach

completes most chemical digestion and is the primary site of nutrient absorption

small intestine

absorbs water and electrolytes, compacts waste into feces, and houses beneficial bacteria

large intestine (colon)

stores feces before elimination.

rectum

controls the release of feces from the body

anus

beak food into smaller pieces (mechanical digestion)

teeth

moves food, forms a bolus, and helps with swallowing

tongue

produce saliva to lubricate food and begin carbohydrate digestion

salivary glands

produces bile, which helps digest fats

liver

stores and concentrates bile, then releases it into the small intestine

gallbladder

produces digestive enzymes and bicarbonate for the small intestine; also produces insulin and glucagon

pancreas

chewing—the mechanical breakdown of food in the mouth by the teeth with the help of the tongue

what is mastication?

breaks food into smaller pieces (mechanical digestion), mixes food with saliva, which begins carbohydrate digestion, forms a bolus (a soft ball of food) that is easier to swallow, increases the surface area of food, making chemical digestion by enzymes more efficient

function of mastication

accessory digestive glands that produce and secrete saliva into the mouth

what are salivary glands?

• parotid glands – located in front of and below each ear

• submandibular glands – located beneath the lower jaw (mandible)

• sublingual glands – located under the tongue

where can salivary glands be found?

• moistens and lubricates food, making it easier to chew and swallow

• forms a bolus for swallowing

• begins chemical digestion of carbohydrates with the enzyme salivary amylase, which starts breaking down starch into smaller sugars

• helps clean the mouth and dissolves food chemicals so they can be tasted

how does saliva aid in digestion?

• nasopharynx – behind the nasal cavity

• oropharynx – behind the oral cavity (mouth)

• laryngopharynx – behind the larynx and continues into the esophagus

what are the three portions of the pharynx?

oropharynx and laryngopharynx

which portion of the pharynx move food?

a soft, rounded mass of chewed food mixed with saliva that is ready to be swallowed

what is a bolus?

oropharynx → laryngopharynx → esophagus

where does the bolus enter after the oral cavity?

after the esophagus, the bolus passes through the lower esophageal (cardiac) sphincter and enters the stomach

where does the bolus go after the esophagus?

• temporarily store food

• mechanically digest food by churning and mixing it

• chemically digest proteins using hydrochloric acid (HCl) and the enzyme pepsin

• mix food with gastric juices to form chyme, which is then released into the small intestine

general function of the stomach

mucosa (innermost layer)

what tunic contains the gastric glands?

secrete HCl, pepsinogen, mucus, and intrinsic factor

gastric glands

three layers of smooth muscle in its muscularis externa (most of the digestive tract has only two)

• outer longitudinal layer

• middle circular layer

• inner oblique layer (unique to the stomach)

in the stomach, how many sublayers of the muscularis tunic are there?

• HCl → kills bacteria and activates pepsin

• pepsin → digests proteins

• mucus → protects the stomach lining

• intrinsic factor → needed for vitamin B₁₂ absorption

• water → helps form chyme

gastric juices are comprised of…

temporary folds of the stomach's mucosa and submucosa

what are the rugae of the stomach?

allow the stomach to expand as it fills with food, flatten during digestion, increasing the stomach's capacity while facilitating the mixing and breakdown of food

what do rugae do during digestion?

secrete pepsinogen and gastric lipase

chief cells

secrete hydrochloric acid (HCl) and intrinsic factor, which is required for vitamin B₁₂ absorption in the small intestine

parietal cells

pepsinogen is the inactive precursor (zymogen) of pepsin, hydrochloric acid (HCl) converts pepsinogen into pepsin, the active enzyme that begins protein digestion in the stomach, once activated, pepsin also activates additional pepsinogen molecules, accelerating protein digestion

relationship between pepsinogen and pepsin

pyloric sphincter

what structure (valve) controls the release of chyme from the stomach?

duodenum, jejunum, ileum

what are the three sections of the small intestine?

first and shortest section of the small intestine; it receives chyme from the stomach and mixes it with bile and pancreatic juices to begin chemical digestion

duodenum

major site of nutrient absorption

jejunum