A&P Test 2 Flashcards

Increased stroke volume

Cooperation of heart, blood vessels, kidneys and supervision by brain

Cardiac output
Peripheral resistance
Blood Volume
*Changes in one variable are quickly compensated for by changes in other variables

CO (ml/min) = SV (ml/beat) x HR (beats/min)
Norman CO = 5.0-5.5 L/min

Venous return, neural controls, hormonal controls

Cardioinhibitory Center via parasympathetic vagus nerves

Venous return (EDV)

increases HEART RATE and STROKE VOLUME via SYMPATHETIC STIMULATION

INCREASES via action on SA NODE

INCREASES via enhancement of contractility

*ESV decrease (less blood in left ventricle)

-Increased activity of respiratory pumps (ventral body cavity pressure)
-Increased activity of muscular pump (skeletal muscle)
-Increased sympathetic venoconstriction
Then...
-Increased venous return
Then...
-Increased EDV
Then..
Increased stroke volume
Results in...
-Increased Cardiac output

A)
-Increased sympathetic activity
Then...
-Increased epinephrine in blood
Then..
-Increased contractility of cardiac muscle
Then...
-Decreased ESV
Then..
-Increased Stroke volume
Results in...
-Increased Cardiac output

B)
-Decreased parasympathetic activity
Then...
-Increased heart rate
Results in...
-Increased Cardiac output

1) Short-term Regulation
2) Long-term Regulation

1) Neural (nervous) control
2) Hormonal (endocrine) controls

-Changing peripheral resistance
-Changing cardiac output

-Renal control

-Changing blood volume

Cardiac Output and Peripheral Resistance

1) Alter blood vessel diameter
-If blood volume is low, all vessels constrict
-Except those to heart and brain
2) Alter blood distribution to organs
-In response to specific demands
-Blood is shunted from digestive tract to skeletal muscles during exercise

Reflex arcs that involve...
-Baroreceptors (stretch receptors)
-Cardiovascular center of medulla oblongata (vasomotor center)
-Autonomic vasomotor fibers to heart and vascular smooth muscle
-Sometime input from chemoreceptors and higher brain centers

Sympathetic neuron
*Causes changes in CO and blood vessel diameter

-Cardiac Centers
.Cardioacceleratory (sympathetic)
--> SA node, AV node, myocardium
--> Increases heart rate and force of contraction
.Cardioinhibitory (parasympathetic)
--> Vagus nerve --> SA node, AV node
--> Decreases heart rate
-Vasomotor Center
--> Regulates diameter of blood vessels

Baroreceptors
Chemoreceptors
Higher brain centers

(pressure-sensistive mechanoreceptors)
-Respond to changes in arterial pressure and stretch

Blood levels of carbon dioxide, H+, and oxygen

Include - Cerebral cortex, limbic system, hypothalamus
respond to exercise, stress, emotions, body temperature

- Carotid Sinuses (dilations in internal carotid arteries --> Major blood supply to brain)
- Aortic Arch
- Walls of large arteries of neck and torax

1) Cause arterioles to dilate
.By inhibiting vasomotor center
.This decreases peripheral resistance
2) Cause veins to dilate
.By inhibiting vasomotor center
.This decreases venous return and cardiac output
3) decrease heart rate and contractile force
.By inhibiting sympathetic (cardioacceleratory) activity and stimulating parasympathetic (cardioinhibitory) activity
.This decreases cardiac output

Increase in CO2
Decrease in pH
Decrease in O2 (sudden drop)

-Cardioacceleratory center
-->Causes increased cardiac output

-Vasomotor center
-->Causes vasoconstriction (sympathetic

Medulla oblongata

Hypothalamus
Cerebral cortex
Limbic system
-->Via relays to medulla oblongata

Increase

Mediates redistribution of blood flow during exercise and body temperature changes

-Epinephrine/norepinephrine
-Angiotensin II
-Antidiuretic Hormone

Increase CO & vasoconstriction
Released from adrenal medulla during stress

Vasoconstriction
Low BP
Kidneys release renin

Kidneys conserve more water causing vasoconstriction when BP falls to dangerously low levels (hemorrhage)
*Released from hypothalamus/posterior pituitary

Atrial Natriuretic Peptide (ANP)

It is released from the heart
Antagonizes aldosterone --> causes kidneys to excrete more sodium and water --> decreases blood volume and BP
*Also causes generalized vasodilation

Regulating blood volume

1. Direct renal mechanism

2. Indirect renal mechanism
---> (Renin-angiotensin-aldosterone mechanism)

Hormones

Elimination of more urine due to increased filtration --> Decreases blood volume and BP

Kidneys to conserve water --> increases blood volume and BP

Renin-angiotensin-aldosterone mechanism

--> Release of renin (enzyme) from kidneys

--> Renin causes production of angiotensin II
.Angiotensinogen (plasma protein)
-Renin
.Angiotensin I
-Angiotensin converting Enzyme (ACE)
.Angiotensin II

-Adrenal cortex to secrete aldosterone
.Increases reabsorption of sodium/water by kidneys

-Stimulates posterior pituitary to release ADH
.Increases water reabsorption by kidneys

-Stimulates hypothalamic thirst center
.Increases water consumption

vasoconstriction
--> Increases peripheral resistance

Modifying diameter of arterioles feeding capillaries

varying resistance of own arterioles

1) Metabolic (chemical) controls
-Responds to changing levels of chemicals
2) Myogenic (physical) controls
-Respond to stretch

– Respond to changing levels of chemicals
– Vasodilation of arterioles and relaxation of precapillary sphincters caused by:
• Decreased tissue O2
• Increased H+, CO2, lactic acid, K+, adenosine, prostaglandins
• Inflammatory chemicals (histamine, kinins, prostaglandins)
• Nitric oxide (NO) – major controller of vasodilation
– Released by vascular endothelium (can override sympathetic)

– Vasoconstriction is caused by:
• Endothelins released from endothelium (to prevent blood loss in injury)

Keep tissue perfusion constant despite changes in systemic pressure
• Increased intravascular pressure promotes vasoconstriction
– Decreases blood flow to the tissue
• Decreased intravascular pressure promotes vasodilation
– Increases blood flow to the tissue

Occurs when short-term autoregulation cannot meet tissue nutrient requirements

Develops over weeks or months

– Number of vessels to region increases
– Existing vessels enlarge
– Common in
• Heart when coronary vessel partially occluded
• Throughout body in people in high-altitude areas

greater metabolic activity -->

– Increased metabolic activity causes decreased O2 and increased metabolic wastes
– Metabolic controls cause relaxation and dilation
of skeletal muscle arterioles to supply more O2 and nutrients to muscles

divert blood to skeletal muscles
– Sympathetic activity increases with exercise
--> vasoconstriction of digestive/urinary tracts

– Blood vessels are inadequately filled
– Blood cannot circulate normally
• Results in inadequate blood flow to meet tissue needs --> cells die

-Hypovolemic shock
-Vascular shock
-Cardiogenic shock

large-scale blood or fluid loss
– Hemorrhage, burns, severe vomiting or diarrhea

extreme vasodilation and decreased peripheral resistance
– Anaphylaxis, septicemia

an inefficient heart cannot sustain adequate circulation
– Myocardial damage

Returns excess interstitial fluid and leaked plasma proteins
back to circulatory system (~3 L per day)

• Lymphatic vessels (lymphatics)
• Lymph – fluid in vessels
• Lymph nodes – cleanse lymph as passes

Spleen, thymus, tonsils, Peyer's patches, appendix, and lymphoid tissues

House phagocytic cells and lymphocytes

Structural basis of immune system

Lymphatic capillaries
Collecting lymphatic vessels
Lymphatic trunks
Lymphatic ducts

Lymph flows toward the heart

• Weave between tissue cells and capillaries
• Absent from bones, teeth, bone marrow, and CNS
• Similar to blood capillaries, except:
– Blind-ended
– Very permeable
• Proteins, cell debris, pathogens, cancer cells enter lymphatics

– Endothelial cells overlap loosely
• Form one-way, flaplike minivalves
– Collagen filaments anchor endothelial cells to surrounding structures
• Prevent collapse of capillaries
• Open minivalves when interstitial fluid volume/pressure increases

Lymphatics
--> Lymph nodes serve to "cleanse" and "examine"

– Specialized lymph capillaries present in
small intestinal villi
– Absorb digested fat and deliver fatty lymph (chyle) to the blood

– Have thinner walls
– Have more internal valves
– Anastomose more frequently

superficial veins

arteries

individuals

Uniion of largest collecting vessels

large areas of the body

– Lumbar
– Bronchomediastinal
– Subclavian
– Jugular trunks

Intestinal trunk

2
Right Lymphatic duct
Thoracic duct
*Lymph is delivered into either of the ducts

Right arm and right side of head and thorax

rest of body
-Superiorly, it drains left thorax, left arm, and left side of head

Cisterna chyli
– Enlarged sac anterior to first two lumbar vertebra
– Collects lymph from legs and digestive organs

Venous circulation
– At junction of internal jugular and subclavian veins
– On its own side of body

– Milking action of skeletal muscle
– Pressure changes in thorax during breathing
– Valves that prevent backflow
– Pulsations of nearby arteries
– Contractions of smooth muscle in walls of lymphatic vessels

lymphocytes

The main warriors of the immune system
-Arise in red bone marrow

– T cells (T lymphocytes)
– B cells (B lymphocytes)

antigens
– Anything the body perceives as foreign and that provokes an immune response
• Bacteria, bacterial toxins, viruses, cancer cells,
mismatched RBCs

– Manage immune response
– Attack and destroy infected cells

– Produce plasma cells
• Which secrete antibodies

– Phagocytize foreign substances
– Help activate T cells

– Capture antigens
– Deliver them to lymph nodes

– Produce reticular fiber stroma
• Network supporting other cells in lymphoid organs

proliferation site for lymphocytes

lymphocutes/macrophages

Reticular connective
– Macrophages live on fibers
– Lymphocytes squeeze through postcapillary venules, rest in lymphoid spaces, then return to blood
• Movement allows lymphocytes to reach infected or damaged tissues

1. Diffuse lymphoid tissue
2. Lymphoid follicles

– Scattered lymphoid cells and reticular fibers
• In ~ every body organ
– Larger collections in lamina propria of mucous membranes (digestive tract)

– Solid, spherical bodies
• Of tightly packed lymphoid cells and reticular fibers
– Germinal centers of proliferating B cells
• Plasma cells --> antibodies
– May form part of larger lymphoid organs or nodes
– Isolated aggregations in intestinal wall (Peyer's patches) and in appendix

Lymph nodes

connective tissue

lymphatic vessels

Inguinal region
Axillary region
Cervical region

Filtration
– Filter lymph as it is transported
– Macrophages destroy microorganisms and debris so they don’t enter bloodstream

Immune system activation
– Lymphocytes become activated and mount
attack against antigens

• Bean shaped
• External fibrous capsule
• Trabeculae (connective tissue strands)
extend inward
– Divide node into compartments
• Two histologically distinct regions
– Cortex
– Medulla

- Lymphoid follicles with germinal centers (with dividing B cells)
- Dendritic cells surround follicles
– Rest of cortex is primarily T cells in transit
• T cells circulate continuously among blood, lymph nodes, and lymph

Cortex

B Cells
T Cells
Plasma Cells

macrophages

afferent lymphatic vessels

large subcapsular sinus and smaller sinuses to medullary sinuses

efferent lymphatic vessels

Stagnates flow which allows lymphocytes and macrophages time to function

Thymus

They help protect the body but do not filter lymph
-Have efferent lymphatics
-No afferent lymphatics

• Largest lymphoid organ
• Structure
– Fibrous capsule and trabeculae
– White pulp - contains lymphocytes
– Red pulp – contains macrophages, many old erythrocytes
• Served by splenic artery and vein (enter/exit at its hilum)

– Site for lymphocyte proliferation
– Immune surveillance and response
– Cleanses blood of:
• Aged/defective blood cells and platelets
• Debris and foreign matter
– Removed by macrophages

• Stores breakdown products of RBCs
– For later reuse
– Iron to make more hemoglobin
• Stores blood platelets and monocytes
– For release into blood when needed
• May be site of fetal erythrocyte production (normally ceases before birth)

early in life
– T lymphocyte presursors mature into immunocompetent lymphocytes

inferior of neck
– Extends into mediastinum
– Partially overlies heart

Newborns
– Increases in size during first year
– Most active during childhood
– Gradually atrophies after puberty
• Becomes fibrous and fatty tissue
– Still produces immunocompetent cells, though slowly

• Bilobed
• Thymic lobules - outer cortex, inner medulla
• Most thymic cells are lymphocytes
• Cortex contains rapidly dividing lymphocytes and scattered macrophages
• Medulla contains fewer lymphocytes and
thymic corpuscles
– Concentric whorls of keratinized epithelial cells
– Involved in development of regulatory T cells (prevent autoimmunity)

• Has no follicles because it lacks B cells
• Does not directly fight antigens
– Functions only in T lymphocyte maturation
• Blood thymus barrier
• Keeps bloodborne antigens out of thymus to prevent premature activation of lymphocytes

• Stroma made of epithelial cells
(not reticular fibers)

Mucosa-Associated Lymphoid Tissue

• Lymphoid tissues in mucous membranes
• Protects from pathogens trying to enter body
• Largest collections of MALT in
– Tonsils
– Peyer's patches – Appendix
• Also in mucosa of respiratory and genitourinary organs and rest of digestive tract

tonsils

lymphatic

At posterior end of oral cavity

At base of tongue

in posterior wall of nasopharynx
• “Adenoids”

surround openings of auditory tubes into pharynx

They gather and remove pathogens in food or air

• Follicles with germinal centers
• Not fully encapsulated
• Overlying epithelium invaginates forming tonsillar crypts
– Trap and destroy bacteria and particulate matter
– Immune cells build memory for pathogens
• Fighting pathogens in childhood leads to increased immunity later in life

Peyers patches and appendix

-In wall of distal small intestine (ileum)

– Tubular appendage at beginning of large
intestine

– Destroy bacteria, preventing them from breaching intestinal wall
– Generate "memory" lymphocytes

To return excess interstitial fluid and leaked plasma proteins back to circulatory system and allow the tissue fluid to be filtered by the lymph nodes

Fluid

Provide structural basis of immune system
House phagocytic cells and lymphocytes
Include spleen, thymus, tonsils, and other lymphoid tissues

One-way system – lymph flows to the heart

Endothelial cells overlap loosely → form one-way, flaplike minivalves
Collagen filaments anchor endothelial cells

Pathogens

Bones, teeth, bone marrow and CNS

Specialized lymph capillaries present in small intestinal villi
They absorb digested fat and deliver fatty lymph (chyle) to the blood

Similar to veins, except:
-Have thinner walls
-Have more internal valves
-Anastomose more frequently
Collecting vessels in skin travel with superficial veins
Deep vessels travel with arteries
Distribution of lymphatic vessels varies between individuals

Lumbar
Bronchomedialstinal
Subclavian
Jugular Trunks

Intestinal Trunk

Right lymphatic duct
Drains right arm and right side of head and thorax
Thoracic duct
Drains rest of body

Thymus

Houses and provides proliferation site for lymphocytes
Surveillance vantage point for lymphocytes/macrophages
Composed mainly of reticular connective tissue
Two main types:
Diffuse lymphoid tissue
Lymphoid follicles

- Diffuse lymphoid tissue:
Scattered lymphoid cells and reticular fibers
In apporoximately every body organ
Larger collections in lamina propria of mucous membranes

- Lymphoid Follicles (nodules)
Solid, spherical bodies of tightly packed lymphoid cells and reticular fibers
May form part of larger lymphoid organs or nodes

Spleen, thymus, tonsils

Inguinal region
Axillary Region
Cervical Region

Filtration
Immune system activation

Bean shaped
External fibrous capsule
Two histologically distinct regions:
Cortex
Medulla

Allows lymphocytes and macrophages time to function

Lymph Nodes

Spleen
Structure:
Fibrous capsule and trabeculae
White pulp – contains lymphocytes
Red pulp – contains macrophages, may old erythrocytes
Served by by splenic artery and vein (enter/exit at its hilum)

Removes old and damaged RBCs
Site for lymphocyte proliferation
Immune surveillance and response

Development of T cells

Lymphocytes

Thymus has no follicles because it lacks B cells
Does not directly fight antigens
Stroma made of epithelial cells

Mucosa-Associated Lymphoid Tissues
Lymphoid tissues in mucous membranes
Protects from pathogens trying to enter body
Largest collections of MALT:
Tonsils
Peyer’s Patches
Appendix

Palatine Tonsils – At posterior end of oral cavity
Lingual Tonsils – At base of tongue
Pharyngeal Tonsils – in posterior wall of nasopharnyx (adenoids)
Tubal Tonsils – Surrond opening of auditory tissues into pharynx

- Trap and destroy bacteria and particulate matter
- Immune cells build memory for pathogens (fighting pathogens in childhood leads to increased immunity later in life)

- Trap and destroy bacteria and particulate matter
- Immune cells build memory for pathogens (fighting pathogens in childhood leads to increased immunity later in life)

In wall of distal small intestine (ileum)

Tubular appendage at beginning of large intestine

- Destroy bacteria, preventing them from breaching intestinal wall
- Genterate “memory” lymphocytes

Alimentary Canal - Gastroentestinal (GI) tract
Accessory Digestive Organs

Teeth
Tongue
Gallbladder
Digestive glands
-Salivary Glands
-Liver
-Pancreas

– Muscular tube from mouth to anus
– Digests food and absorbs nutrients
– Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

1. Ingestion
2. Propulsion
3. Mechanical Breakdown
4. Digestion
5. Absorption
6. Defecation

taking food into digestive tract via the mouth

movement of food through GI tract

reduction of food to smaller pieces to increase surface area for digestion

chemical breakdown of food by enzymes

active or passive transport of nutrients, vitamins, minerals, and water from GI tract lumen into blood or lymph

elimination of indigestible substances from the body via the anus in the form of feces

Adjacent segments of alimentary tract organs alternately contract and relax, moving food along the tract distally. Major means of propulsion.

Nonadjacentsegments of alimentary tract organs alternately contract and relax, moving food forward then backward. Food mixing and
slow food propulsion occurs

Mechanoreceptors and Chemoreceptors
Intrinsic and extrinsic controls

In the walls of GI tract

Stretch
Changes in osmolarity and pH
Presence of substrate and end products of digestion

• Activate or inhibit digestive glands
• Stimulate smooth muscle to mix and move contents

– Nerve plexuses (“gut brain”) respond to stimuli in GI tract to regulate GI tract activity via short reflexes

– CNS centers and autonomic nerves respond to stimuli inside or outside GI tract via long reflexes

– Stomach and small intestine release hormones
that stimulate target cells in same or different organs, causing them to secrete or contract

– Serous membrane of abdominal cavity
– Visceral peritoneum covers external surfaces of most digestive organs
– Parietal peritoneum lines body wall

– Narrow space between the two peritoneums
– Serous fluid lubricates organs

- double layer of peritoneum
– Extends from body wall to digestive organs
– Routes for blood vessels, lymphatics, and nerves
– Holds organs in place
– Stores fat

- partially surrounded
– Lie against posterior abdominal wall
– Pancreas, duodenum, part of large intestine

– Completely surrounded by peritoneum

lose their mesentery and move,
becoming retroperitoneal, during development.

Greater Omentum
Lesser Omentum
Falciform ligament
Mesentery Proper
Mesocolon

“fatty apron”
– Extends from greater curvature of stomach
– Covers most abdominal organs

– Connects lesser curvature of stomach and proximal duodenum to liver

- Attaches the lier to the anterior abdominal wall

– Fan-shaped peritoneum that suspends jejunum and ileum from posterior abdominal wall

– Attaches large intestine to posterior abdominal wall

• Arteries
– Hepatic, splenic, left gastric arteries
• Branches of celiac trunk
• Supply corresponding organ
– Inferior mesenteric artery
• Supplies small intestine
– Superior mesenteric artery
• Supplies large intestine

• Hepatic portal circulation
– Drains nutrient-rich blood from digestive organs
– Delivers it to the liver for processing

– Mucosa
– Submucosa
– Muscularis externa
– Serosa

• Innermost layer that lines the lumen
• Functions
– Secretes mucus, digestive enzymes, hormones
– Absorbs end products of digestion
– Protects against infectious disease

-Epithelium
-Lamina Propria
-Muscularis mucosae

– Simple columnar epithelium with mucus-secreting cells
– Exception – stratified squamous in mouth, esophagus, anus
– Mucus protects from enzymes and eases food passage
– May synthesize and secrete enzymes and hormones
• Stomach and small intestine

– Loose areolar connective tissue
– Capillaries for nourishment and absorption of nutrients
– Lymphoid follicles (part of MALT) defend against pathogens

– Thin layer of smooth muscle

• Areolar connective tissue
• Rich supply of:
– Blood vessels
– Lymphatic vessels
– Lymphoid follicles
– Nerve fibers
– Elastic fibers (in stomach for stretching)

• Composed of two layers of smooth muscle
– Inner circular
• Thickens in some areas to form sphincters
– Outer longitudinal layer
• Responsible for segmentation and peristalsis

• Visceral peritoneum
• Areolar connective tissue
– Covered with mesothelium in most organs
• Simple squamous epithelium
• Replaced by adventitia in esophagus
– Fibrous connective tissue

• Intrinsic nerve supply of alimentary canal regulates digestive system activity - enteric neurons
• Linked to CNS via afferent visceral fibers
• Long ANS fibers synapse with enteric plexuses
– Sympathetic impulses inhibit digestive activities
– Parasympathetic impulses stimulate digestive activities

– In submucosa
– Regulates glands and smooth muscle in mucosa

– Between circular and longitudinal layers of muscularis
– Controls GI tract motility

• Bounded by lips, cheeks, palate, tongue
• Oral orifice is anterior opening
• Lined with stratified squamous epithelium
– Produces defensins – antimicrobial peptides

– Orbicularis oris (lips) and buccinator (cheeks) muscles
– Vestibule - recess bounded externally by lips and cheeks, internally by teeth and gums (gingiva)
– Labial frenulum – median fold that attaches lip to gum

teeth and gums

Roof of the mouth

– Formed by palatine bones and palatine processes of maxillae
– Midline ridge - raphe
– Mucosa is slightly corrugated to create friction against tongue during chewing

– Fold formed mostly of skeletal muscle
– Rises and closes nasopharynx during swallowing
– Uvula projects downward from its free edge

Skeletal muscle

– Positioning of food between teeth
– Mixing of food with saliva
– Formation of bolus (compact mass of food) – Initiation of swallowing
– Speech production
– Taste

– Attaches tongue to floor of mouth and limits posterior movements

Surface bears papillae (peglike projections of underlying mucosa)
-Filiform papillae
-Fungiform papillae
-Circumvallate (vallate) papillae
-Foliate Papillae

– smallest and most numerous
– Contain keratin – stiffens and makes tongue whitish
– Roughens tongue surface/provides friction to manipulate foods
– Do not contain taste buds

- reddish, mushroom shaped
– Scattered over tongue
– Contain taste buds

– ten to twelve
– V-shaped row at back of tongue
– Contain taste buds

– pleatlike, on lateral aspect of posterior tongue
– Contain taste buds that function only in infants and children

on the tongue

– Just posterior to vallate papillae
– Groove that marks division between
• Body - anterior 2/3 tongue in oral cavity
• Root - posterior third of tongue in oropharynx
– Mucosa covering root of tongue lacks papillae
• Bumpy due to lingual tonsil deep to mucosa

– Secreted by serous cells beneath foliate and vallate papillae
– Fat-digesting enzyme that becomes functional in acid of stomach

Oral cavity

ducts

- Parotid
- Submandibular
- Sublingual

Are scattered though out oral cavity mucosa

salivary output

– Cleanses the mouth
– Dissolves food chemicals for taste
– Moistens food
– Compacts food into bolus
– Begins chemical breakdown of starch

– Parasympathetic nervous system
• Stimulates secretion of saliva
– Sympathetic nervous system
• Inhibits secretion of saliva

– Anterior to ear and external to masseter muscle
– Parotid duct parallels zygomatic arch
• Duct opens into vestibule next to second upper molar
– Facial nerve branches run through parotid gland
• Parotid surgery may cause facial paralysis
– Mumps virus causes inflammation of parotid glands

– Medial to body of mandible
– Duct opens at base of lingual frenulum

– Anterior to submandibular gland under tongue
– Opens via 10–12 ducts into floor of mouth

• Mostly water and slightly acidic
– Electrolytes (Na+, K+, Cl–, PO4 2–, HCO3–) – Salivary amylase
– Lingual lipase
– Mucin – forms mucus in water
• Lubricates oral cavity and hydrates food
– Metabolic wastes (urea and uric acid)
– Lysozyme – bacteriocidal enzyme
• Inhibits bacterial growth and prevents tooth decay
– IgA antibodies
– Defensins

Teeth TEAR and GRIND food for digestion

21

maxillary artery and trigeminal nerve (cranial nerve V)

– Chisel shaped for cutting

(cuspids or eye-teeth) – Fanglike teeth that tear or pierce

– Broad crowns, rounded cusps – grind/crush

– Broad crowns, rounded cusps – best grinders

- exposed part above gum (gingiva)
– Covered by enamel—hardest substance in body
– Calcium salts and hydroxyapatite crystals

- portion embedded in jawbone
– Connected to crown by neck (constricted region)

- calcified connective tissue
– Covers root
– Attaches tooth to periodontal ligament

– Forms fibrous joint called gomphosis
– Anchors tooth in bony socket (alveolus)

- groove where gingiva borders tooth

- bonelike material under enamel
– Maintained by odontoblasts of pulp cavity
• Produced throughout life

- Surrounded by dentin

-connective tissue, blood vessels, nerves

– extension of pulp cavity into root

- at proximal end of root
– Entry for blood vessels and nerves

One root
-First upper premolar often has two

Three roots

Two roots

It varies
-Usually single fused root

Demineralization of enamel and dentin from bacterial action
– Dental plaque adheres to teeth
• Film of sugar, bacteria, and debris
– Bacterial metabolism produces acids that dissolve calcium salts
– Bacterial enzymes digest organic matter
– Prevention - daily flossing and brushing

- red, swollen, sore, bleeding gums
– Plaque calcifies to form calculus (tartar)
• Disrupts seal between gingivae and teeth
– Anaerobic bacteria infect gums
– Infection reversible if calculus removed

neglected gingivitis
– Immune cells attack intruders and body tissues
• Destroy periodontal ligament
• Activate osteoclasts

Mouth --> Oropharynx --> Laryngopharynx

Food, fluids, and air

• Stratified squamous epithelium (inner lining)
– Mucus-producing glands

– Inner longitudinal
– Outer pharyngeal constrictors
• Contractions propel food into esophagus

• Flat muscular tube
• From laryngopharynx to stomach
• Pierces diaphragm at esophageal hiatus • Joins stomach at cardial orifice
• Gastroesophageal (cardiac) sphincter
– Surrounds cardial orifice
– Reinforced by presence of diaphragm

– Stomach acid regurgitates into esophagus
– Excess food/drink, extreme obesity, pregnancy, running

– Hiatal hernia - structural abnormality
• Part of stomach protrudes above diaphragm
–Weakened gastroesophageal sphincter
• May lead to esophagitis, esophageal ulcers, esophageal cancer

- stratified squamous epithelium
– Changes to simple columnar at stomach

– Secrete mucus to aid in bolus movement
Areolar connective tissue

– Skeletal muscle in superior 1/3
– Mixture of skeletal and smooth in middle
– Smooth muscle in last 1/3
-Has a circular layer and longitudinal layer

fibrous connective tissue– Instead of serosa

• Mouth
– Ingestion
– Mechanical digestion (breakdown)
• Chewing (mastication)
– Propulsion
• Swallowing (deglutition)
– Chemical digestion
• Salivary amylase - begins digestion of carbohydrates
• Lingual lipase (activated by stomach acid)
– No absorption occurs in mouth (except for few drugs)
• Pharynx and esophagus
– Sole function is propulsion of food
• Transport of food from mouth to stomach

=Swallowing
Involves 22 muscles

- Voluntary
- Occurs in mouth
- Tongue contracts to force bolus into oropharynx

During the buccal phase, the upper esophageal sphincter is contracted.
The tongue presses against the hard palate and contracts, forcing the food bolus into the oropharynx.

– Involuntary – begins when tactile receptors in posterior pharynx are stimulated by bolus
– Controlled by medulla and pons
– Vagus nerve transmits motor impulses from swallowing center to muscles of pharynx and esophagus

The pharyngeal-esophageal phase begins as the uvula and larynx rise and the epiglottis bends to prevent food from entering respiratory passageways. The tongue blocks off the mouth. Upper esophageal sphincter relaxes, allowing food to enter the esophagus.

the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after food enters.

esophagus to the stomach

cardial oriface opens, and food enters the stomach

• Located in upper left quadrant

• Functions:
– Food storage
– Begins digestion of proteins – Converts food into chyme

Cardial orifice

esophagus

Dome-shaped region beneath the diaphram

midportion

– funnel-shaped region near duodenum
– Pyloric antrum (superior portion) --> pyloric canal --> pylorus
– Pyloric sphincter - controls stomach emptying

- Convex lateral surface

- Concave medial surface

Branches of celiac trunk

hepatic portal vein

Folds of lining seen when stomach is empty

-Lesser omentum
– From liver to lesser curvature

-Greater momentum
– From greater curvature
--> drapes anteriorly over small intestine
--> wraps spleen & transverse colon
--> blends with mesocolon
- Contains fat deposits & lymph nodes

mucosa, submucosa, muscularis, serosa
-Muscularis and mucosa modified

– Three layers of smooth muscle (instead of two)
– Inner oblique layer allows stomach to churn, mix, move, and physically break down food

– Simple columnar epithelium
• Composed of mucous (goblet) cells
– Dotted with gastric pits --> gastric glands
• Gastric glands produce gastric juice

– Pepsinogen - activated to pepsin by HCl & by pepsin itself (a positive feedback mechanism)
– Lipases - digest lipids

acids and enzymes

• Thick layer of bicarbonate-rich mucus
• Tight junctions between epithelial cells
– Prevent juice seeping underneath tissue
• Damaged epithelial cells are quickly replaced by division of stem cells
– Surface cells replaced every 3–6 days

– Inflammation of stomach wall caused by anything that breaches mucosal barrier

– Erosions of stomach wall
• Can perforate --> peritonitis and hemorrhage
– Most caused by Helicobacter pylori bacteria

• Physical digestion
• Denaturation of proteins by HCl
• Enzymatic digestion of proteins by pepsin
– Protein digestion begins in the stomach
• Lingual lipase becomes activated and digests some triglycerides before it is digested
• Delivers chyme to small intestine
– Chyme – partially digested food and gastric juice

• Neural and hormonal mechanisms
• Vagus nerve stimulation-->secretion increases
• Sympathetic stimulation --> ecretion decreases
• Hormonal control is mainly gastrin
– Stimulates enzyme and HCl secretion
– Stimulates most small intestine secretions - gastrin antagonists

1. Cephallic (reflex) phase
2. Gastric Phase
3. Intestinal phase

*before food enters stomach
– Conditioned reflex triggered by sight, smell, taste, or thought of food
– Sensory receptors --> hypothalamus --> medulla oblongata --> vagus nerve --> enteric neurons --> stimulates glands

– lasts 3–4 hours (2/3 gastric juice released)
– Stimulated by distension, peptides, low acidity (high pH), gastrin (major stimulus)
– Caffeine, peptides, rising pH (from ingested proteins) stimulate enteroendocrine G cells to release gastrin
– Gastrin stimulates parietal cells to release HCL
– HCL digests proteins

-Stimulatory component
-Inhibitory component

• Partially digested food enters duodenum
• Duodenum releases intestinal (enteric) gastrin
– To blood --> stomach
– Stimulates gastric glands to continue secretions

• Intestine distends with chyme
– Chyme contains H+, fats, peptides, irritating substances
• Distension of intestine
– Inhibits gastric activity
» To protect small intestine from excessive acidity
– Causes pyloric sphincter to tighten
» To prevent further food entry

– Acetylcholine (ACh)
• Released by parasympathetic nerve fibers
– Gastrin
• Secreted by G cells in stomach
– Histamine
• Released by enteroendocrine cells of glands
–In response to gastrin
• Antihistamines block histamine receptors of parietal cells --> decrease HCl --> decrease ulcers

gastroesophageal sphincter
--> gentle rippling

Peristaltic waves STRENGTHEN and move toward PYLORUS at rate of 3 per MINUTE

Contractile rhythm set by enteric pacemaker cells located in longitudinal smooth muscle layer

Gap junctions --> entire muscularis contracts

force of contractions

3 ml spurts to duodenum

1) Propulsion: Peristaltic waves move from the fundus toward the pylorus.

2) Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus.

3) Retropulsion: The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum, simultaneously forcing most of its contained material backward into the stomach.

• As chyme enters duodenum
– Receptors respond to stretch and chemical signals
– Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling
• Enterogastrones = secretin, cholecystokinin, vasoactive intestinal peptide

• Stomach usually empties completely within four hours after a meal
• Carbohydrate-rich chyme moves quickly through duodenum
• Fatty chyme remains in stomach 6 hours or more

The small intestine

superior mesenteric artery

Veins --> superior mesenteric vein --> hepatic portal vein --> liver -->
inferior vena cava --> heart

– Duodenum (retroperitoneal)
– Jejunum (attached posteriorly by mesentery)
– Ileum (attached posteriorly by mesentery)
• Joins large intestine at ileocecal valve

• Shortest part – 25 cm (10 inches)
• Curves around head of pancreas
• Bile duct (from liver) and pancreatic duct (from pancreas)
– Join at hepatopancreatic ampulla
– Enter duodenum at major duodenal papilla
– Hepatopancreatic sphincter controls entry of bile and pancreatic juice (Sphincter of Odi)

• Highly adapted for absorbing nutrients
• Wall has three structural modifications to increase surface area for absorption (primarily in proximal part)
– Circular folds (plicae circulares)
– Villi
– Microvilli

Circumferential --> force chyme to slowly spiral through lumen (speed bumps)

– Fingerlike projections (~1 mm high) of mucosa
– Capillary bed and lacteal in center of each villus

– Extensions of plasma membrane of columnar epithelial cells lining small intestine
– Contain brush border enzymes that complete digestion of carbohydrates and proteins

– Simple columnar epithelium
• Absorptive cells = enterocytes
• Goblet cells secrete mucus
• Studded with pits between villi
-->tubular glands called intestinal crypts
– Lamina propria
• Capillary and lacteal extend into each villus
– Muscularis mucosa
• Thin layer of smooth muscle

MALT
– Located in lamina propria of mucosa
• May protrude into submucosa
– Prominent in ileum
– Protect against bacteria entering bloodstream

– In submucosa of duodenum
– Secrete alkaline (bicarbonate-rich) mucus to neutralize acidic chyme

• Secreted by epithelial cells of intestinal crypts
– In response to distension or irritation of mucosa
• Slightly alkaline (7.4-7.8)
– Isotonic with blood plasma
• Mainly water with some mucus from mucosa goblet cells and duodenal Brunner’s glands
– Enzyme-poor
(enzymes of small intestine only in brush border)
• Facilitates transport & absorption of nutrients

• Largest gland in body (weighs 3 lbs)
• Four lobes—right, left, caudate, quadrate
• Many metabolic functions
– Important – processes nutrient-laden venous blood from digestive organs
• Only digestive function is bile production
– Bile – fat emulsifier
• Breaks down fats to smaller particles that are more readily digestible

– Separates larger right and smaller left lobes
– Suspends liver from diaphragm and anterior abdominal wall

– Remnant of fetal umbilical vein
– Along inferior edge of falciform ligament

visceral peritoneum
- Except bare area which touches diaphragm

– Common hepatic duct leaves liver
– Cystic duct leaves gallbladder
– Bile duct formed by union of common hepatic and cystic ducts

• Produce bile (900 ml per day)
• Process bloodborne nutrients
– Store glucose as glycogen
– Use amino acids to make plasma proteins
• Store fat-soluble vitamins
• Perform detoxification
• Participate in Vitamin D synthesis

• Yellow-green, alkaline solution containing
– Bile salts - cholesterol derivatives that function in fat emulsification and absorption
– Bilirubin - pigment formed from heme
• Bacteria in small intestine break down to stercobilin --> brown color of feces

– Cholesterol
– Triglycerides
– Phospholipids
– Electrolytes

Bile salts

– Recycles bile salts (3-5 times per meal)
– Bile salts --> duodenum --> reabsorbed from ileum --> hepatic portal blood --> liver secreted into newly formed bile

• Thin-walled muscular sac on ventral surface of liver
• Stores and concentrates bile by absorbing water and ions
• Releases bile into cystic duct, which flows into bile duct

• Bile is major means of cholesterol excretion from body
• Bile salts keep cholesterol dissolved in bile
• High cholesterol or too few bile salts
--> cholesterol crystalizes
--> gallstones (biliary calculi)
• Gallbladder contracts against crystals --> pain
• Gallstones obstruct bile flow
--> may cause obstructive jaundice

• Mostly retroperitoneal
• Deep to greater curvature of stomach

• Head - encircled by duodenum
• Tail - touches the spleen
• Body – mid portion of gland
• Uncinate process – folded posteriorly

Produces enzymes that break down all food categories

– Pancreatic islets = Islets of Langerhans
• Secrete insulin and glucagon

– Acini secrete pancreatic juice
• Acini - clusters of secretory acinar cells
• Zymogen granules of acini cells contain inactive digestive enzymes (proenzymes)

– Pancreatic juice empties into the duodenum via main pancreatic duct

acinar cells

• Watery alkaline solution (pH 8)
– Neutralizes acidic chyme that enters duodenum
– Optimal environment for intestinal & pancreatic enzymes
• Electrolytes (primarily HCO3– , --> raises pH)
• Enzymes
– Secreted in active form
• Amylase – digests starch
• Lipase – digests fats
• Nuclease - digests nucleic acids
– Secreted in inactive form and activated in duodenum
• Proteases - digest proteins
– Trypsinogen --> trypsin -->
» Chymotrypsinogen --> chymotrypsin
» Procarboxypeptidase --> carboxypeptidase

increased bile salts* in enterohepatic circulation
• Causes liver to produce more bile

• Secretin released from intestinal cells (duodenum)
–Exposed to acidic fatty chyme

• Stimulates pancreatic release of HCO3 rich juice
• Inhibits gastric secretions and motility

digestion is active

continuously

Bile backs up to GALLBLADDER when sphincter CLOSED
--> bile stored in gallbladder

gallbladder contracts

Cholecystokinin (cck)***
• Released from intestinal cells in response to acidic, fatty chyme entering duodenum
– Parasympathetic vagal stimulation (minor)

– Stimulates secretion of enzyme-rich pancreatic juice
– Relaxes hepatopancreatic sphincter
• Allows bile & pancreatic juice to enter duodenum
– Inhibits gastric secretion and motility

1. Chyme entering duodenum causes duodenal enteroendocrine cells to release cholecystokinin (CCK) and secretin.

2. CCK (red dots) and secretin (yellow dots) enter the bloodstream.

3. CCK induces secretion of enzyme-rich pancreatic juice. Secretin causes secretion of HCO3− -rich pancreatic juice.

4. Bile salts and, to a lesser extent, secretin transported via bloodstream stimulate liver to produce bile more rapidly.

5. CCK (via blood stream) causes gallbladder to contract and hepatopancreatic sphincter to
relax. Bile enters duodenum.

– Partially digested carbohydrates and proteins
– Undigested fats

• 3–6 hours in small intestine
– Most water and virtually all nutrients absorbed

• Digestion requires:
– Slow delivery of acidic, hypertonic chyme
– Delivery of bile, enzymes, and bicarbonate ions from liver, gallbladder, and pancreas
– Mixing

• Most substances needed for SI digestion originate outside the SI & are delivered to the SI
– Bile
– Digestive enzymes (most)
– Bicarbonate ions
• Brush border enzymes of SI microvilli complete digestion of carbohydrates, proteins, & nucleic acids

* Anything that impairs liver, gallbladder, or pancreatic function or delivery of their substances hinders digestion

• Smooth muscle activity in small intestinal wall has three primary functions:
– Mixes chyme with accessory gland secretions
– Brings chyme in contact with brush border
of mucosa
– Propels contents toward large intestine
• Accomplished by segmentation & peristalsis

– Most common motion of small intestine*
– Initiated by intrinsic pacemaker cells
– Mixes chyme with digestive secretions
– Helps bring chyme in contact with mucosa
– Moves contents toward ileocecal valve
– Intensity altered by long & short reflexes and by hormones
• Parasympathetic increases ; Sympathetic decreases
– Wanes in late intestinal (fasting) phase

– Initiated by rise in motilin hormone
• Released by duodenal mucosa
• In late intestinal phase (after most nutrients absorbed)
• Starts in proximal duodenum every 90–120 minutes
– Each successive wave starts distal to previous
• Migrating motor complex (MMC)
– Propels meal remnants, bacteria, and debris to large intestine
• “Housekeeping function” --> sweeps to LI
– From duodenum to ileum ~ 2 hours

constriced

– Gastroileal reflex (triggered by stomach activity) increases force of segmentation in ileum
– Gastrin (released by stomach) increases motility of ileum

Ileocecal valve flaps CLOSE when chyme exerts BACKWARD PRESSURE
– Prevents regurgitation into ileum

• Absorbs water (not absorbed by SI)
• Absorbs vitamins produced by bacterial flora
• Absorbs electrolytes (mainly Na+ and Cl-)
• Temporarily stores digestive residues
• Eliminates indigestible material from body as feces
• The colon is not essential for life

• Teniae coli
– Three bands of longitudinal smooth muscle in
muscularis (act like elastic)

• Haustra
– Pocketlike sacs caused by tone of teniae coli

• Epiploic appendages
– Fat-filled pouches of visceral peritoneum that
hang from surface (unknown significance)

Cecum
Appendix
Colon
Rectum
Anal Canal

(“blind pouch”) – first part of LI – Ileocecal valve

– fingerlike projection attached to posteromedial surface of cecum
– Contains masses of lymphoid tissue
• Part of MALT of immune system
– Bacterial storehouse
--> recolonizes gut when necessary
– Structure allows enteric bacteria to accumulate and multiply --> appendicitis

– Ascending colon (right side)
- Right colic (hepatic) flexure
– Transverse colon
- Left colic (splenic) flexure
– Descending colon (left side)
– Sigmoid colon (S-shaped in pelvis)
– Ascending colon and descending colon are retroperitoneal
– Transverse and sigmoid colon are intraperitoneal and anchored to posterior abdominal wall by mesocolons

– Joins sigmoid colon at level of third sacral vertebra
– Three rectal valves stop feces from being passed with gas (flatus)

- last segment of large intestine
– Lies external to abdominopelvic cavity
– Opens to body exterior at anus
– Two sphincters
• Internal anal sphincter - smooth muscle, involuntary
• External anal sphincter - skeletal muscle, voluntary

Simple columnar epithelium
– Except in anal canal (stratified squamous – abrasion)

• No circular folds or villi
• No cells that secrete digestive enzymes
– Because food is digested and absorbed before reaching large intestine

• Abundant deep crypts with GOBLET CELLS***
– Mucus eases passage of feces and protects mucosa
from irritating bacterial acids and gases
• Superficial venous plexuses (hemorrhoidal veins) of anal canal form hemorrhoids if inflamed

• Most bacteria are killed before enter LI
• Enter from small intestine or anus
– Colonize colon
– Synthesize B complex vitamins and vitamin K
– Ferment indigestible carbohydrates (cellulose)
– Release irritating acids and gases (flatus)
• Prevented from breaching mucosal barrier by IgA response of MALT

• Periodic inflammation of intestinal wall
• Abnormal immune response to normal bacterial antigens
• Linked to newly discovered helper T cell and deficits of
lysozymes, defensins etc secreted by gut mucosa
• Symptoms – cramping, diarrhea, weight loss, bleeding
• Two subtypes:
– Ulcerative colitis – shallow inflammation, mainly rectum
– Crohn’s disease – more serious, with deep ulcers and fissures in entire intestine, but mostly terminal ileum

diet, antibiotics, anti-inflammatory drugs, immunosuppressant drugs, stress reduction

Mass movements force feces toward rectum
Muscles of rectum contract to expel feces
Assisted by Valsalva's maneuver

• Digestion
– Catabolic process that breaks down large molecules to monomers small enough to be absorbed

• Uses enzymes secreted by intrinsic and accessory glands
• Enzymatic breakdown occurs by hydrolysis – Water is added to break bonds

***Most digestion and absorption occurs in the small intestine

• Carbohydrates must be broken down to monosaccharides to be absorbed
– Glucose, fructose, galactose
• Begins in mouth
– Salivary amylase
• Continues in small intestine
– Pancreatic amylase
– Brush border enzymes of small intestine

• Proteins digested include
– Dietary proteins, enzymes, and mucosal cells
• Begins in stomach
– Pepsinogen secreted by chief cells of stomach is activated to pepsin (by HCl and pepsin itself)
• Inactivated by high pH of duodenum
• Continues in small intestine
– Pancreatic enzymes
• Trypsin, chymotrypsin, carboxypeptidase
– Brush border enzymes

• Very small amount (10%) of fat is digested by lingual lipase after it is activated in stomach
**Small intestine is primary site of lipid digestion**
– Pancreatic lipase
• Fats must be emulsified for efficient digestion
– Broken down in duodenum to smaller fat droplets by bile salts contained in bile from liver

• Does not break chemical bonds
• Reduces attraction between fat molecules
• Disperses fat molecules
• Increases exposure to pancreatic lipases
• Fatty acids and monoglycerides associate with bile salts
to form micelles

• Occurs in small intestine
• Pancreaticnucleases
– Ribonuclease & deoxyribonuclease
– Hydrolyze to nucleotide monomers
• Intestinal brush border enzymes
– Nucleosidases and phosphatases
• Break nucleotides apart to release
–Nitrogenous bases
–Pentose sugars
–Phosphate ions

***Almost all food, 80% electrolytes, and 95% water are absorbed in small intestine
***Most absorption complete before chyme reaches ileum
• All that remains at end of ileum is
– Small amount of water
– Indigestible food materials (cellulose)
– Bacteria!!!
***Ileum’s major absorptive role is to reclaim bile salts
to be recycled back to liver
– Enterohepatic circulation

• Most nutrients are absorbed by active transport
– Enter villus capillaries
– Transported by hepatic portal vein to liver (processed)
– Empties into inferior vena cava

• Exception – lipids
– Absorbed by passive diffusion
– Enter lacteals in villi of small intestine
– Enters blood at junction of left internal jugular vein and subclavian vein

• Gluten-sensitive enteropathy (celiac disease)
– Immune reaction to gluten
• Protein in all grains except corn and rice
– Gluten complexes with immune system molecules
• Immune complexes attack intestinal lining
–Damage intestinal villi and brush border
– Bloating, diarrhea, pain, malnutrition
– Treated by eliminating gluten from diet

• Most dietary vitamins absorbed by small intestine
• Large intestine absorbs some of Vitamin K and B vitamins made by its enteric bacteria
• Fat-soluble vitamins (A, D, E, K) dissolve in dietary fats and are absorbed by passive diffusion
– Enter lacteals
– Thus must eat fatty food to absorb these vitamins
• Vitamin B12 absorption requires intrinsic factor produced by the stomach