Anatomy Notes Week 7 PDF

Lymphatic (Lymphoid) System 1. Lymphatic vessels Vessel network that collects excess interstitial fluid (and proteins) that leaks out of capillaries and returns it (now termed lymph) back to the bloodstream  forms a one-way drainage system a) lymphatic capillaries – series of blind-ending tubes ad...

Lymphatic (Lymphoid) System 1. Lymphatic vessels Vessel network that collects excess interstitial fluid (and proteins) that leaks out of capillaries and returns it (now termed lymph) back to the bloodstream  forms a one-way drainage system a) lymphatic capillaries – series of blind-ending tubes adjacent to tissue cells and capillary beds b) lymphatic collecting vessels  thin-walled vessels with one-way valves  the lymph is filtered of bacteria/cellular debris as it passes through (macrophage & lymphocyte containing) lymph nodes Lymphatic System c) lymphatic ducts – empty lymph back into circulation i) thoracic duct – begins as an enlarged lymph vessel (cisterna chyli) in the abdomen  collects lymph from below the ribs and the entire left side of body; drains into the left subclavian vein ii) right lymphatic duct – collects lymph from right upper body; enters circulation via the right subclavian vein Lymph flow towards the heart driven by: i) skeletal muscle pump – movement ii) respiration (pressure changes in thoracic cavity) 1 Lymphatic System 2. Lymphoid organs and tissues – contain many lymphocytes; play a key role in the body’s immune system A) Primary lymphoid organs and tissues – sites where lymphoid stem cells divide and mature (become immunocompetent) i) red bone marrow  lymphoid stem cells originate here during fetal development  site of B lymphocyte proliferation (mitosis) and maturation ii) thymus gland – some lymphoid stem cells migrate to here in the fetal stage, where they mature into T lymphocytes and multiply Lymphatic System B) Secondary lymphoid organs and tissues – where most lymphocyte immune responses occur  sites of T & B lymphocyte activation and proliferation i) lymph nodes – small masses of lymphatic tissue  large clusters found in cervical (neck), axillary (armpit), and inguinal (groin) regions ii) spleen  helps filter (cleanse) blood of old cells, bacteria, viruses, and cellular debris iii) mucosal-associated lymphoid tissue (MALT)  includes tonsils, appendix, lymphoid tissues on mucosal membranes of digestive, respiratory, reproductive, and urinary systems 2 iii) mucosal-associated lymphoid tissue (MALT) Tonsils form a ring around the entrance to the pharynx  possess crypts that also trap bacteria and debris a) pharyngeal tonsil – called ‘adenoids’ when enlarged  found in the posterior nasopharynx palatine tonsils b) paired palatine tonsils  in the oropharynx; commonly removed* lingual tonsil c) lingual tonsil (nodular)  lumpy follicles on the base of the tongue Respiratory System Main Functions: 1. Ventilation  the movement of air into and out of the lungs 2. Gas exchange  transfer of O2 and CO2 between the lungs and the blood nasal cavity Two subdivisions: nose A. Upper respiratory system trachea  nose, nasal cavity, pharynx B. Lower respiratory system pharynx larynx bronchial tree  larynx, trachea, bronchial tree, lungs lungs 3 Respiratory System Structures bone 1. Nose upper cartilage  supported by bone and hyaline cartilage lower cartilage nares  nostrils (‘nares’) 2. Nasal cavity  right and left sides are separated by the nasal septum ethmoid anterior septum (cartilage) a) anterior part – hyaline cartilage b) posterior part – ethmoid, vomer, palatine, and maxillae bones maxillae vomer palatine Nasal cavity Functions of nasal cavity: a) airway passage; warm, moisten, and filter air b) olfaction (smell) c) resonance chamber for speech Areas: i) nasal vestibule (anterior)  surrounded by cartilage  lined by skin with coarse hairs ii) respiratory area (posterior) iii) olfactory area 4 ii) Respiratory area Lined by respiratory mucosa  pseudostratified cilated columnar epithelium resting on the lamina propria (CT)  contains many goblet cells (secrete mucus) Nasal glands in the underlying CT layer also secrete mucus together with antimicrobial enzymes Thin, scroll-like projections (conchae) protrude medially from each lateral wall of the nasal cavity: superior middle superior project from ethmoid middle inferior inferior – a separate bone ii) Respiratory area Air passes through grooves (meatuses) formed between the conchae  turbulent airflow here helps humidify air and trap dust on the ciliated epithelium A (naso)lacrimal duct is located between the the external eye and the inferior nasal meatus  drains tears into the nasal cavity lacrimal duct inferior nasal meatus 5 iii) Olfactory area Essential for smell  located on the roof of the nasal cavity Formed mostly by ciliated pseudostratified columnar epithelium  lacks columnar cell goblet cells, though is interspersed with neurons containing olfactory receptors olfactory neuron Respiratory System Structures 3. Paranasal sinuses  pairs of air-filled spaces in the: i) frontal ii) ethmoid iii) sphenoid iv) maxillae frontal sinus ethmoidal sinus nasal cavity sphenoidal sinus maxillary sinus All open directly into the nasal cavity Help warm and moisten air; reduce density of the skull (i.e. mass per unit of volume) Sinusitis: inflammation of mucus membrane in the sinuses 6 Respiratory System Structures 4. Pharynx (throat) pharynx Skeletal muscle lined by mucous membrane Divided into three regions: a) nasopharynx Air passage posterior to the nasal cavity; air enters via paired nasal apertures  also connects ears via the paired pharynogotympanic (Eustachian) tubes Pharyngeal tonsil is on the posterior wall Mucosa is ciliated pseudostratified columnar epithelium 4. Pharynx b) oropharynx Air and food passage posterior to the oral cavity; from the soft palate to the epiglottis  contains the palatine tonsils and the lingual tonsil c) laryngopharynx Air and food passage from the epiglottis to the opening of the larynx b) and c) are both lined by stratified squamous epithelium 7 Respiratory System Structures 5. Larynx (voice-box) Air passage connecting the pharynx to the trachea Composed of eight hyaline cartilages and one non-hyaline cartilage (epiglottis): larynx i) single cartilages a) epiglottis  elastic cartilage that covers the glottis while swallowing b) thyroid cartilage (‘Adam’s apple’)  on the anterior wall larynx c) cricoid cartilage  forms a complete ring around the larynx 5. Larynx ii) paired cartilages  form part of the lateral and posterior larynx a) arytenoid cartilages  anchors vocal cords to the posterior wall b) two other pairs (don’t need to know names) Vocal cords (ligaments) – located in the mid-larynx  two sets of paired folds under the laryngeal mucosa i) vestibular folds (‘false’ vocal cords)  the superior fold  helps close the glottis when swallowing 8 Vocal cords ii) vocal fold (= true vocal cords)  the inferior fold  produce sound by vibration The glottis includes the vocal fold and the opening between the upper and lower larynx  closes upon swallowing to prevent food and liquids from entering the trachea Laryngitis: inflammation of the larynx due to infection or irritation Respiratory System Structures 6. Trachea (windpipe) An air passage anterior to the esophagus that connects the larynx to the primary (1°) bronchi that enter each lung  mucosa = ciliated pseudostratified columnar epithelium with globet cells The trachea contains 20 “C-shaped” pieces of hyaline cartilage  the open section of each “C” (posterior) faces the esophagus, permitting it to expand anteriorly when swallowing 9 Respiratory System Structures 7. Bronchial tree: ~23 generations of branches Extends from the primary bronchi to the alveolar ducts branch # Walls: decreasing amount of hyaline cartilage increasing amount of smooth muscle 7. Bronchial tree Epithelium: ciliated pseudostratified columnar Walls: primarily composed of smooth muscle and elastic fibers (no cartilage) Two (1°) bronchi (1 to each lung) 2 5 lobar (2°) bronchi (3 on right, 2 on left) simple non-ciliated squamous/ cuboidal 3 4 13 generations of segmental bronchi (3º, 4º, 5º, etc.) 5 15 1° bronchi 2° bronchi 3º-15º bronchi many terminal bronchioles ciliated simple cuboidal 1 more respiratory bronchioles more alveolar ducts ‘conducting zone’ (‘anatomical dead space’) branch # 16 3-5 mm 23 ‘respiratory zone’ (site of gas exchange) millions of alveoli 10 8. Lungs Alveoli (~150 million/lung); polyhedral in shape Form part of the respiratory membrane  two epithelial layers fused to a central basement membrane O2 CO2 alveolar epithelium Respiratory membrane capillary epithelium  the membrane is moist, thin (~0.5 µm), and is perfused by the respiratory capillaries  primary site of gas exchange (simple diffusion) (O2: alveoli → blood plasma; CO2: plasma → alveoli) 40X 8. Lungs The respiratory membrane is formed by: a) the alveolus wall i) type I alveolar cells (simple squamous) type II cell type I cell capillary wall alveoli type I basement membrane type II cells capillaries ii) type II cells (simple cuboidal)  secrete surfactant; reduces water tension in alveoli (helps you breathe easier) b) a fused alveolar/capillary basement membrane c) the capillary wall  simple squamous epithelium (‘endothelium’) 11 8. Lungs Macrophages enter the alveoli from the blood, where they help to remove bacteria and other debris (e.g. dust) Clinical applications: A) Tuberculosis (‘TB’; ‘consumption’); fibrotic lung disease Infectious disease caused by Mycobacterium tuberculosis Lung tissue replaced by fibrous CT (collagen ‘scars’)  decreases lung elasticity (harder to inhale)  thickens the respiratory membrane  decreases the surface area for gas exchange Clinical applications B) Pulmonary edema Accumulation of fluid in the lungs  between cells and within the alveoli  impairs gas exchange C) Pulmonary embolism Blockage of pulmonary vasculature  due to lodged blood clots, fat, air bubbles or tumors in lung blood vessels embolism 12 Respiratory membrane D) Pneumothorax Entry of air into the pleural cavity surrounding a lung  causes that lung to collapse (the other lung is generally unaffected) E) Emphysema; obstructive lung disease normal emphysema  destruction and collapse of alveoli and smaller airways (decreases surface area)  causes large increase in airway resistance due to loss of elastic fibres (makes it harder to exhale; decreases gas exchange per breath) 8. Lungs Gross morphology: The lungs are separated by the mediastinum Right lung: three lobes  superior, middle, inferior Left lung: two lobes  superior, inferior  has a cardiac notch (where heart lies) Smooth muscle within the lung bronchi is innervated by the autonomic nervous system (to dilate/constrict bronchi) 13 8. Lungs Pleura (serous membrane):  surround each lung and connect them to the thoracic cavity wall a) parietal pulmonary pleura attached to the inner thoracic wall, superior diaphragm, and mediastinum b) visceral pulmonary pleura attached to the lung surface These membranes form plural cavities filled with serous fluid  reduces friction during ventilation 8. Lungs Blood supply: A) Pulmonary route  for alveolar oxygenation of blood right ventricle pulmonary trunk deoxygenated right and left pulmonary arteries alveolar capillaries pulmonary veins oxygenated left atrium 14 Blood supply B) Bronchial route; subdivision of the systemic circulation  carries O2 to lung tissues (e.g. bronchial walls, pleura) bronchial arteries left ventricle alveoli aorta bronchial arteries bronchial vein vena cava pulmonary vein bronchial tissues (except alveoli) bronchial veins vena cava pulmonary veins right atrium left atrium Note: most blood is shunted back to the pulmonary circuit 8. Lungs Ventilation is via skeletal muscles: A) Inspiration  diaphragm (moves inferiorly) and external intercostals (elevate ribs) contract B) Expiration  relaxation of diaphragm and external intercostals  passive recoil of lungs The rate and depth of breathing are controlled by the medulla and dependent on blood CO2 and O2 levels (and emotions) 15