lecture exam 3

Functions of lymphatic system

• Consists of lymphatic vessels, nodes, & lymphoid tissue

• Includes cells, tissues, & organs responsible for:

  • Maintaining normal blood volume & composition of interstitial fluid

  • ​Immunity

  • ​Absorption of lipids (digestive system)

Maintaining normal blood volume & composition of interstitial fluid

• Assist in the circulation of body fluids

• Drains & cleans excess fluid from interstitial spaces & returns to blood

​Immunity

• Transports & house lymphocytes & other immune cells

• Ability to fight infection, illness, & disease

• Two complementary mechanisms

  • Innate

  • Adaptive

Primary lymphoid structures

• Lymphocytes form or mature from

  • Red bone marrow 

  • Thymus         

Secondary lymphoid structures

• Lymphoid organs & aggregates of lymphoid nodules

• House lymphocytes & other immune cells

• Site where immune response begins; lymphocytes activated & copied

Innate Immunity

• Born with

• Non-specific defense

• Acts relatively quickly

• Physical & chemical barriers

• Phagocytes

Adaptive Immunity

• Develop via exposure to pathogens

• Needs more time to react

• Antibody mediated (B cells)

• Mark w/ antibodies

• Cell mediated (T cells)

• Attack cells directly

White blood cells (WBC)

•   Located between trabeculae of spongy bone in long bones

•   Site of hematopoiesis: production of formed elements

Types of lymphocytes

B and T

B lymphocytes/B cells

• Antibody-mediated immunity

  • Develop & mature in red bone marrow

  • Move to lymph, nodes, spleen, & other lymphoid tissue

​T lymphocytes/T cells

•  Cell-mediated immunity

  • Develop in red bone marrow & mature in thymus

  • Travels to peripheral lymphoid tissues & organs

Phagocytes

• engulf/destroy foreign substances, pathogens, & cellular debris

Neutrophils

• abundant, mobile, & fast acting

  • Debris or bacteria

Eosinophils

• Foreign compounds & antibody-coated pathogens

Macrophages

Pathogens, dead cells, & debris

Lymphatic capillaries

• Differ from blood capillaries

• Overlapping endothelial cells

• Typically found near blood capillaries

• Interstitial fluid → lymphatic capillaries = lymph/lymphatic fluid

• Lymphatic capillaries → lymphatic vessels → lymphatic trunks →  lymphatic ducts

How lymphatic capillaries differ from blood capillaries:

• Small, closed at one end

• Larger diameters

• Thinner walls

  • Incomplete or absence basement membrane 

Lymphatic capillaries: Overlapping endothelial cells

• Flaps b/w cells → one-way valve

• Absorbs interstitial fluid; can’t exit

• Takes in viruses, bacteria, & cell debris

Lymphatic vessels

• Fed by lymphatic capillaries

• Located nearby arteries & veins

• All 3 tunic layers (intima, media, & externa); structurally similar to veins

• Valves

• Low pressure; lymph moves

• Some connect to lymph nodes = lymph filtration

All 3 tunic layers (intima, media, & externa); structurally similar to veins valves

• Prevent pooling & back flow of lymph

• Found in small & medium-sized lymphatic vessels

• Vessels bulges at each valve: ~ a string of pearls

Low pressure in LV; lymph moves by

• Skeletal muscles & respiratory pumps

• Pulsing blood in nearby arteries

• Contraction of smooth muscle in larger lymph vessel walls

Lymphatic trunks

• fed by lymphatic vessels

  • Left & *right jugular trunks

    • Drain lymph from head & neck

  • Left & *right subclavian trunks 

    • Drain upper limbs, breasts, & superficial thoracic wall

  • Left & *right bronchomediastinal trunks 

    • Drain deep thoracic structures

  • Intestinal trunk

    • Drain most abdominal structures

  • Left & right lumbar trunks 

    • Drain lower limbs, abdomino-pelvic wall, & pelvic organs

*empties into right lymphatic duct

Left & *right jugular trunks

Drain lymph from head & neck

Left & *right subclavian trunks

Drain upper limbs, breasts, & superficial thoracic wall

Left & *right bronchomediastinal trunks

Drain deep thoracic structures

Intestinal trunk

Drain most abdominal structures

Left & right lumbar trunks

Drain lower limbs, abdomino-pelvic wall, & pelvic organs

Lymphatic ducts

• Largest lymph vessels

• Form when superficial & deep lymphatics converge

• Form two:

  1. ​Thoracic

  2. ​Right lymphatic
     

Thoracic duct

• Drains body inferior to diaphragm & left side of body 

• Then empties into left subclavian vein

Right lymphatic duct

• Drains right side of body, superior to diaphragm (* trunks from prior slide)

• Empties into right subclavian vein

Lymph nodes

• Found in chains along larger lymphatic vessels 

• Large lymph nodes: neck, groin, & axillae

• Filters & removes 99% of pathogens from lymph; before enter bloodstream

• Small, oval, encapsulated structures 

  • Outer fibrous capsule

  • Trabeculae: fibrous partitions; divides into compartments; packed w/ lymphocytes

• Cortex

• Inner medulla

Lymph nodes cortex

• Composed of lymphoid nodules

• B cells & macrophages proliferate

• Surrounding mantle zone contains T cells, macrophages, & dendritic cells

• Cortical sinuses: channels; lined w/ macrophages

lymph nodes inner medulla

• Medullary cords: CT fibers; supports B & T cells & macrophages

• Medullary sinuses: tiny open channels; lined w/ macrophage

Lymph pathway

• Several ​afferent lymphatic vessels bring lymph to node

• Lymph flows through node

  • Monitored for presence of foreign material 

  • Macrophages remove foreign debris

  • Lymphocytes may initiate immune response

    • Causing increase is specific lymphocytes

    • Resulting in enlarged, hardened nodes, typically in the neck, axilla, & groin regions

• Exit: single efferent lymphatics 

  • Leaves via the hilum, w/ BVs & nerves

  • May then enter a neighboring lymph node

• Occur in clusters receiving lymph from body regions

  • Cervical lymph nodes receive lymph from head & neck

  • Axillary lymph nodes receive lymph from breast, axilla, & upper limb

  • Inguinal lymph nodes in groin receive lymph from lower limb & pelvis  

Cervical lymph nodes receive lymph from:

Head and neck

Axillary lymph nodes receive lymph from:

Breast, axilla, & upper limb

Inguinal lymph nodes in groin receive lymph from:

Lower limb & pelvis

Lacteals

• Within small intestine

  • Prominent lymphatic capillaries

  • Lipids absorbed & transported from gi tract

  • Lipids unable to enter blood directly; needs to be emulsified by bile first

  • Chyle: milky substance of lymph & emulsified fats or free fatty acids

  • → lymph vessels → circulating blood

Chyle

Milky substance of lymph & emulsified fats or free fatty acids

Non-encapsulated lymphoid tissues

incomplete or no capsule

• Mucosa-associated lymphoid tissue (MALT) 

• Peyer’s patches

• Tonsils

Encapsulated lymphoid tissue

• Fibrous capsule of dense irregular CT

• Outer cortex 

• Inner medulla

  • Lymph nodes

  • Thymus

  • Spleen

• Phagocytes 

  • Remove foreign substances & pathogens

MALT

• Mucosa-associated lymphoid tissue

• Clusters of lymphoid cells with some extracellular matrix

• Diffuse & unencapsulated lymphoid tissue: scattered nodules

• Help defend against infection

• Densely packed w/ lymphocytes

  • Lamina propria of mucosa (areolar tissue)

  • Located in gastrointestinal, respiratory, genital, & urinary tracts

• In some areas, group together to form larger structures

MALT structures

• Peyer’s patches

  • Large collections of diffuse lymphoid nodules 

  • Within walls of the ileum

• Appendix

  • Destroy remaining bacteria; prevents breach of intestinal wall

• Tonsils

  • Masses of lymphoid tissue in mucosa & submucosa

Tonsils

• Incomplete protective ring around entrances of respiratory & digestive systems

• Masses of lymphoid tissue within mucosa & submucosa

• Tonsillar crypts: invaginations; trap & kill pathogens

  • Contains lymphoid nodules

  • B & T cells & macrophages

• Largest size at puberty; then ↓ in size

Pharyngeal tonsil (adenoids)

Superior wall of nasopharynx

Palatine tonsils (left & right)

Pair; posterolateral oral cavity

Lingual tonsils

Pair; base of tongue

Thymus

• Located in the anterior mediastinum, above heart

• Huge role in acquired immunity

• Soft, bi-lobed organ

  • Maturation site of T cells

• Divided into left & right lobes w/ CT capsule

  • Lobes divided by fibrous partitions = septa

  • Outer cortex 

    • Regulate T cell development & function

    • Maintains blood-thymus barrier

    • Immature T cells leave ~3 weeks 

  • Inner medulla

    • Mature T cells

• Larger in children than adults

• Grows until puberty, then regresses; gradually replaced by adipose tissue

• Size & secretory abilities decline with age

  • 40 g before puberty; <12 g, ~ 50 yo 

  • ↓ in size as age ↑ & becomes more fibrous (involution)

  • ↑ in susceptibility to disease

Spleen

• Largest lymphatic organ

• Filled with blood instead of lymph

• Monitors & filters blood

  • Removes abnormal RBCs, platelets, & foreign particles

  • Stores recycled iron from RBCs

  • Initiates immune response to circulating antigens by B-cells & T-cells

  • Produces blood for first 5 months of fetal life

• Outer capsule: collagen & elastic fibers

  • Fairly easily ruptured by impact

• If too damage; unable to repair surgically = splenectomy; w/o spleen: ↑ risk of bacterial infection

• Path of flow: splenic artery → central artery → sinusoids → venules → splenic vein

Hilum

indentation; nerves, BVs & lymphatic vessels enter; gastrosplenic ligament

Trabeculae

• Fibrous partitions; hilum → capsule 

• Divides red & white pulp

• Allow room for blood vessels

Pulp

• Cellular components within capsule

• ID & remove pathogens & damaged or infected cells in bloodstream

• Red

• White

Red pulp

• Splenic sinusoids: very permeable capillaries

• Lots of macrophages, T & B cells

• Macrophages in sinusoids of red pulp

• Phagocytize bacteria, debris, defective RBCs & platelets

White pulp

• Monitors for foreign materials & bacteria

• Contains T cells, B cells & macrophages around central artery

• Similar to lymph nodules

Functions of respiratory system

• Air passageway: atmosphere → alveoli

• Site for exchange of oxygen & carbon dioxide

• Protect respiratory surfaces: dehydration, temperature changes & pathogens

• Sound production

• Detection of odors

Upper respiratory system

• Nose, nasal cavity, pharynx, & larynx

• Filters, warms, & humidifies incoming air

• Protects delicate lower tract

• Reabsorbs heat & water from outgoing air

Nose and nasal cavity

Primary route for air entering respiratory system

• External nares/nostrils

• Nasal septum

• Nasal vestibule

• Choanae/internal nares

• Hard palate

• Soft palate

• Superior, middle, & inferior nasal conchae (bones)

• Superior, middle, & inferior nasal meatuses (passages)

External nares/nostrils

paired openings into nasal cavity

Nasal septum

vomer, perpendicular plate of the ethmoid, & hyaline cartilage

Nasal vestibule

space at front of nasal cavity; coarse hairs trap large particles

Choanae/internal nares

opening into nasopharynx

Hard palate

bony floor; separates from oral cavity

Soft palate

posterior fleshy part

Superior, middle, & inferior nasal meatuses (passages)

• Swirl incoming air; trap small particles

• Moves chemicals to olfactory receptors

• Warms/humidifies air

Pharynx

Shared by respiratory & digestive systems

1. ​Nasopharynx

2. ​Oropharynx

3. ​Laryngopharynx

​Nasopharynx

1. superior to soft palate

• Pharyngeal opening of auditory tubes

• Lined by pseudostratified ciliated columnar epithelium

​Oropharynx

2.  from soft palate to base of tongue

• Lined by nonkeratinized stratified squamous epithelium

Laryngopharynx

3. hyoid to larynx or esophagus

• Lined by nonkeratinized stratified squamous epithelium

Larynx

• Cartilaginous (hyaline) tube; surrounds & protects the glottis 

• “Voice box” - houses vocal cords

  • Epiglottis

  • Thyroid cartilage 

  • Laryngeal prominence:

  • Cricoid cartilage

Epiglottis

• protects opening; forms lid; elastic cartilage

• When swallows: larynx elevates; epiglottis folds back, to cover glottis; blocks entry into respiratory tract

Thyroid cartilage

Large, shield shape; lateral & anterior walls of larynx

Laryngeal prominence

• Adam’s apple

• Ligaments: attaches to hyoid bone & other cartilages

Cricoid cartilage

• Complete ring          

• Protects glottis &  larynx; attachment for laryngeal muscles/ligaments

Small paired laryngeal cartilages

1. ​Arytenoid cartilages 

   • Articulate with superior surface of cricoid cartilage

   • Move vocal cords

   • Open/close glottis

Glottis

• Passageway for air through larynx

• Made of vocal folds & rima glottidis (opening b/w folds)

Vocal folds

• tissue folds (mucosa)

  • Surround vocal ligaments (avascular elastic CT)

  • B/w thyroid & arytenoid cartilages

  • Vibrations produce sound waves

  • Opened/closed by rotation of arytenoid cartilages

  • AKA the true vocal cords

Lower respiratory tract

• Trachea, bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts & alveoli

• Conducts air to & from gas exchange surfaces

• Gas exchange: respiratory bronchioles, alveolar ducts, & alveoli

Trachea

• AKA the windpipe

• Starts at C₆ & ends at T₅

• Tough, long, flexible tube from larynx  to main bronchi; in mediastinum

• Convey air towards lungs

• 20 C-shaped tracheal cartilage (hyaline)

  • Keeps airway open/prevents collapse

  • Expands during swallowing

  • Annular ligaments: fibroelastic ligaments  that connect tracheal cartilages

  • Posterior ends connected by trachealis muscle

    • When contract: trachea narrows; restricts airflow

    • Tracheal diameter changes often; sympathetic stimulation; increases airflow

Annular ligaments

• fibroelastic ligaments that connect tracheal cartilages

• Posterior ends connected by trachealis muscle

Bronchial tree (Bronchi)

• Bronchi to bronchioles; branch into smaller tubes; diameter ↓ with each new branch

• Right & left main (primary) bronchi

• Lobar (secondary) bronchi

• Segmental (tertiary) bronchi

Right & left main (primary) bronchi

• To each lung; right bronchus - wider; steeper angle

• Cartilagenous rings (hyaline)

Lobar (secondary) bronchi

• To each lobe; 3 (right), 2 (left)

• Cartilage plates

Segmental (tertiary) bronchi

• To each lung segment

• Cartilage plates

Bronchioles

• Bronchioles → terminal bronchioles →   respiratory bronchioles → pulmonary lobule                                                      

  • No cartilage; thick smooth muscle

  • Bronchodilation: ↑ airflow

  • Bronchoconstriction: ↓ airflow

  • Extreme; allergic reactions, asthma

Alveoli

• Clusters ~150 million/lung

• Open, spongy appearance

• Surrounded by elastic fibers; aids expansion/recoil

• Surrounded by extensive capillary networks

• Gas exchange sites

Alveolar ducts

• lined by simple squamous epithelium

• Thinness facilitates gas exchange

​Conducting portion

• Nose → terminal bronchioles

• Transport air

​Respiratory portion

• Respiratory bronchioles,  alveolar ducts, & alveoli

• Gas exchange

Pleurae

• Serous membrane surrounding lungs

• Simple squamous epithelium + areolar CT

• Visceral pleura

• Parietal pleura

• Pleural cavity

• Pleural fluid

Visceral pleura

covers outer lung surfaces

Parietal pleura

covers inner surface of thoracic wall; extends over diaphragm & mediastinum

Pleural cavity

potential space b/w visceral & parietal layers

Pleural fluid

• serous fluid 

  • Lubricates & reduces friction

  • Produced by serous membranes

  • Drained continuously by lymph

Paranasal sinuses

• frontal sinus, ethmoidal air cells, maxillary sinus, & sphenoidal sinus

  • Connected to nasal cavity 

  • Lined by pseudostratified ciliated columnar epithelium  

  • Mucus moistens/cleans sinuses & nasal cavity surfaces

  • Mucus sweep into pharynx

  • Reduces weight of skull

  • Helps with sound production

  • Sinus infection: inflammation of ducts that drain the sinuses;                                                sinuses do not drain well; increased bacterial growth

Respiratory mucosa

• = mucous membrane: respiratory lining

  • Epithelium resting on a basement membrane with underlying lamina propria

  • Nasal cavity to large bronchioles

  • Pseudostratified ciliated columnar epithelium w/ mucous cells

  • Epithelial stem cells replace damaged/old cells

Lamina propria

• Underlying areolar tissue

• Extensive network of veins

• Supports respiratory epithelium

• Mucous glands (goblet cells) in trachea & bronchi  

• Heats & humidifies inhaled air

• Reabsorbs heat & water in exhaled air  

Mucociliary Escalator

• Mucous cell & mucous glands produce sticky mucus

• Traps debris & pathogens

• Moved by beating cilia

• Swept toward pharynx

  • Swallowed (stomach acids)

  • Coughed out

• EX: cystic fibrosis

Bronchopulmonary segments

• Multiple in each lung

  • Right lung: 10 segments; Left lung: 8-10

  • Encapsulated with CT

  • Supplied with its own segmental bronchus; pulmonary artery & vein; lymph vessels

  • Made up of lobules

    • Supplied w/ a terminal bronchiole; arteriole; venule; & lymph vessel

Lobes

• Cone shaped & divided into lobes by deep fissures

• Divided into lobes

  • Right lung (3)

    • Superior lobe

      • Horizontal fissure

    • Middle lobe

      • Oblique fissure

    • Inferior lobe

  • Left lung (2)

    • Superior lobe

      • Oblique fissure

    • Inferior lobe

Right lung lobes (3)

• Superior lobe

  • Horizontal fissure

• Middle lobe

  • Oblique fissure

• Inferior lobe