ANAT 100: Block Theory 3 (modules 9-12)

What are the two phases of breathing?

1. Inspiration- inhalation- draws oxygen rich air into lungs
2. expiration- exhalation- forces oxygen poor air out of lungs

What is gas exchange?

Movement of gases across membranes

In external respiration- exchange of gases between air and blood

* inspired oxygen moves across cellular membranes of alveolus of lungs and capillaries into blood
* CO2 moves in opposite direction and out of body through expiration

\
In internal respiration- exchanges gases- O2 and CO2 between blood and cells of body

What is gas conditioning?

Gases entering lungs must be conditioned, warmed, cleansed to prevent damage to lungs

Occurs in nasal cavities and paranasal sinuses- air is swirled to become warmed and humidified

Inhaled air is cleansed by contact with mucosal lining of respiratory epithelium

What is sound production?

Singing or speech occurs through forceful expiration of air through vocal chords in larynx, causes them to vibrate

Different tensions of vocal chords produce different sounds- help from teeth, lips, tongue

What is olfaction?

Receptors for smell located within olfactory epithelium on nasal cavity

When air inhaled, airborne molecules dissolve in mucus which lines cavity and stimulates receptors

Signals from receptors travel to brain through olfactory nerve, resulting in sense of smell

What is defense of respiratory system?

Respiratory system has line of defense against molecules that can cause infection

Coarse hair of nostrils, ciliated cells of respiratory epithelium, mucus lining help trap particles and microorganisms from entering nose and respiratory system

What type of epithelium lines respiratory tract?

Pseudostratified ciliated columnar epithelium

What does this epithelium do?

Surface of epithelium covered in cilia- help for air conditioning

Cilia trap inhaled particles and microorganisms caught in mucus, sweep them back up respiratory tract and out through nose and mouth

What can be found within this epithelium?

Gobet cells

* produce mucus, causing them to stain lightly
* mucus from these cells forms protective layer over epithelium and traps particulate matter/microorganisms that may be inhaled
* provides moisture to humidify air

What are the two regions of the respiratory system?

Conducting portion and respiratory portion

What is the conducting portion?

Transfers or conducts inhaled air to to lungs

Where humidification and trapping of debris occurs

No oxygen absorbed into blood here- walls too thick

What are the structures of the conducting portion?

Nose, nasal cavity, paranasal sinuses, pharynx, larynx, trachea, bronchi, terminal bronchioles

What is the respiratory portion?

Transfers gases between lungs and pulmonary capillaries

Pulmonary capillaries- structures in lungs that have thin walls to facilitate movement of gases from air to blood

Gas exchange occurs here

What structures are apart of the respiratory portion?

Respiratory bronchioles

Alveolar ducts

Alveolar sacs

Alveoli

What are the paranasal sinuses?

Collection of air filled sacs within bones of skull, connect with nasal cavity

Aid in conditioning air, defense against pathogens, resonance chambers for speech

Lined with respiratory tract epithelium

8 of them total- paired, frontal, maxillary, ethmoid, sphenoid

What is the nose and nasal cavity?

First line of defense against invading pathogens and debris- traps them in hair and mucus

Air enters nose, passed into nasal cavity to be conditioned

What are the nasal cavity boundaries?

Surrounded by bony structures- 6 boundaries

Roof- ethmoid bone in skull

Floor- hard palate- roof of mouth

Medial wall- nasal septum

Lateral wall- contain nasal conchae (create turbulence in air as it passes through cavity, allows for conditioning and catching debris)

Anterior nares- anterior border of cavity- nostrils

Posterior border- opening to nasopharynx (choanae), where nasal cavity connects to pharynx

What is the histology of the nasal cavity?

Covered in respiratory tract epithelium- because it protects from debris and microorganisms

What is the histology of the nasal cavity?

Roof of nasal cavity lined with olfactory epithelium- contains sensory receptors for smell

Composed of pseudostratified ciliated columnar epithelium and bipolar olfactory receptor neurons

What is the pharynx?

Muscular tube connecting nasal cavity and larynx

Connects oral cavity with esophagus

What are the components of the pharynx?

3 components

Nasopharynx- most superior

Oropharynx- middle aspect, part of respiratory and digestive systems, passes air from nasopharynx and food from oral cavity into larngopharynx

Laryngopharynx- most inferior aspect, involved in both digestive and respiratory systems passes food and air into other systems

What is the histology of the pharynx?

Nasopharynx- mostly respiratory tract epithelium

Oropharynx and laryngopharynx- stratified squamous epithelium

What is the larynx?

Produces sound- voice box

Made up of cartilages, ligaments, muscles

Sits anterior to esophagus, connects pharynx and trachea, prevents food from entering trachea

What cartilages make up the larynx?

Epiglottis

Thyroid cartilage

Cricoid cartilage

What is the epiglottis?

Spoon shape elastic cartilage

Functions to prevent food from passing into trachea

Flips downward during swallowing, covers trachea

What is thyroid cartilage?

Shield that is made of hyaline cartilage

Provides attachment for muscles and vocal chords

Tough, flexible tissue, forms front of larynx

Forms Adam’s Apple

What is cricoid cartilage?

Cricoid- ring of hyaline cartilage

Encircles trachea

Narrow anteriorly, broad posteriorly

Attachment for muscles and vocal chords

What are the vocal chords?

Small ligaments attached to laryngeal cartilages that vibrate when air is forced out of lungs

When they vibrate, sound produced

Different sounds made by altering tension on chords

True and false vocal chords- False are closer to front of mouth

What is the trachea?

Extends from larynx to T4 and T5

Splits at junction- called carina, branches into bronchi

Functions to conduct air to lungs- windpipe

What is the structure of the trachea?

Made up of 15-20 C shaped cartinaginous rings

Rings function to keep airway open

Connected posteriorly by trachealis muscle

What is the histology of the trachea?

Has 3 histological layers


1. Mucosa
* Lined with RTE to clear debris or pathogens that make it into lower respiratory tract
2. Submucosa
* Between mucosa and adventitia
* made up of loose (areolar) connective tissue, contains large vessels and nerves, mucus secreting glands
3. Adventitia
* Outer layer of connective tissue surrounding trachea
* Encloses C-shaped cartilaginous rings made of hyaline cartilage
* Rings make trachea flexible and durable- good because organs in thoracic cavity shift during breathing

What are the primary bronchi?

Splitting of trachea into two primary bronchi

Have same function and histological features as trachea

Each primary bronchus enters respective lung on medial site at hilus

Right primary bronchi= wider, shorter, more vertical

What is the end of the conducting portion?

Bronchi dividing into smaller and smaller tubes

Begin as larger diameter, thick walled tube to smaller diameter, thin walled tube

Primary, secondary, tertiary bronchi and terminal bronchioles

What are the lungs?

Respiratory portion makes up majority of lung tissue within both lungs

Lungs on either side of heart within thoracic cavity

Right lung= bigger than left

What are the characteristics of the right lung?

Three lobes- superior, middle, inferior

Two fissures- separate lobes- horizontal and oblique

What are the characteristics of the left lung?

Two lobes- superior and inferior

* superior lobe- has cardiac notch- depression that accommodates space taken up by apex of heart
* has small outward facing process- lingula

\
One fissure- separates lobes- oblique

What is the apex of the lung?

Most superior point of lung

What is the diaphragmatic surface of the lung?

Sits superiorly to diaphragm, dome shaped skeletal muscle, bottom of lung

What is the costal surface of the lungs?

Curves around lateral surface of lung

What is the mediastinal surface of the lung?

Medial surface, contains entry and exit points for all vessels and airways at hilus

What are the pleural membranes?

Pleura- two continuous membranes that form a sac around each lung

Secretes pleural fluid to fill pleural space between membranes

Fluids= lubricants, allowing visceral pleura of lung to slide on parietal pleura of thoracic wall during inflation and deflation

What are the two pleural membranes?

Parietal pleura and visceral pleura

What is parietal pleura?

Outer serous membrane attached to walls and floor of thoracic cavity around lungs

Continuous with visceral pleura at hilus of lung

What is visceral pleura?

Serous membrane attached to surface of lung that is continuous with parietal pleura at hilus

What are the respiratory bronchioles?

They branch from terminal bronchioles

Smallest airways

First structures that contribute to gas exchange in lungs

Thin walled ducts lined with simple ciliated cuboidal epithelium

Keep branching, end with alveoli

What are alveoli?

Functional unit of lung

Where gas exchange occurs

Each alveolus surrounded by capillaries to maximize amount of oxygen going into body and CO2 leaving body

What groups are organs divided into in the digestive system?

1. Digestive tract- alimentary canal
* mouth, oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anus
2. Accessory digestive organs
* tongue, teeth, salivary glands, liver, biliary ducts, gallbladder, pancreas

What is the digestive tract?

Continuous tube that starts in oral cavity, ends inferiorly with anal canal

Each organ in digestive tract plays role in breakdown of food and uptake of nutrients

What are the functions of the digestive tract?

Digestion

* Mastication crushing good in mouth into smaller pieces, chemical processing of enzymes into smaller molecules

Absorption

* Most absorption occurs in small intestine
* Water, vitamins, etc, absorbed in large intestine

Secretion

* Cells of stomach mucosal wall release gastric acid to perform chemical digestion

Motility

* When food swallowed, muscles in esophageal wall contract and relax to push food through esophagus into stomach

Elimination of waste

* unabsorbed materials eliminated by process of defecation

Where is digestion completed?

Small intestine

What is the histology of the digestive tract wall?

Mucosa

Submucosa

Muscularis externa

Serosa/adventitia

What is mucosa?

Innermost layer of digestive tract wall

composed of 3 elements

* Surface epithelium- secretion, absorption, protection
* Lamina propria- layer of connective tissue under surface epithelium
* Muscularis mucosa- smooth muscle fibres under lamina propria

What is submucosa of digestive tract?

* layer below mucosa
* Dense irregular connective tissue, contains blood vessels, lymphatics, glands, nerve plexuses

What is muscularis externa of digestive tract?

* Circular and longitudinal layers of smooth muscles with nerve plexuses in between layers
* plexuses- responsible for muscular contraction to move food through digestive tract

What is serosa/adventitia of digestive tract?

* Outermost layer of digestive tract is either serosa or adventitia
* When outer layer is serious membrane (single layer, thin, flat)= serosa
* When outer layer is loose connective tissue= adventitia

What is the oral cavity?

First part of digestive tract

Two parts- vestibule (space between cheeks and lips and gums and teeth), oral cavity proper (other areas in mouth)

What is the palate?

Makes up superior border of oral cavity

Divided into hard palate- bone- and soft palate- muscle

Posterior extension of soft palate= uvula

What sets of teeth do we have?

Humans have 2 sets of teeth in lifetime

First set- deciduous teeth- baby teeth

Second set- permanent teeth- important for mechanical digestion of food

What do deciduous teeth consist of?

2 incisors, 1 canine (cuspid), 2 molars in each quadrant of jaw (upper right quadrant)

Total= 20 teeth

What do permanent teeth consist of?

2 incisors, 1 canine (cuspid), 2 molars (bicuspids), 3 molars in each quadrant of jaw

Total= 32 teeth

What is the tongue?

Muscle associated with speech, taste, mechanical manipulation of food

Made up of muscles that control shape of tongue (intrinsic muscles) and muscles that move tongue during chewing, speech (extrinsic muscles)

Inferior surface of tongue= frenulum- anchors tongue to floor of mouth

What are papillae of tongue?

Superior and lateral surfaces of tongue= covered in papillae

Projections or bumps on tongue

4 types

What are the salivary glands?

Secrete digestive enzymes and mucus to break down food while chewing

3 major salivary glands- parotid, submandibular, sublingual

What is the parotid gland?

Secretes serous (watery) fluid

Located anterior and inferior to external ear opening

What is the submandibular gland?

Secretes serous and mucous (viscous) fluid

Inferior to mandible

What is the sublingual gland?

Secretes mucus

Inferior to tongue

What are the tonsils?

Collections of lymphoid tissue found in areas of pharynx

Play a role in immune system

What are the three types of tonsils?

Palatine, pharyngeal, lingual

What is the esophagus?

Follows oral cavity

Muscular tube

25cm in length from pharynx to stomach

What is the histology of the esophagus?

Characterized into 4 layers

Mucosa

Submucosa

Muscularis externa

Serosa/adventitia

What is the mucosa of esophagus?

Stratified squamous epithelium that protects esophagus from friction as food travels from oral cavity to stomach

What is submucosa of esophagus?

Contains secreting glands

Secreted mucus is transported through duct to be deposited in lumen of esophagus

Mucus will then lubricate tract to allow for food to pass easier

What is the muscularis externa of the esophagus?

Has both smooth and skeletal muscle

upper 1/3rd= skeletal

middle 1/3rd= skeletal and smooth

lower 1/3rd= smooth muscle

What is the serosa/adventitia of the esophagus?

Majority of esophagus covered by adventitia- loose connective tissue

What are the regions of the stomach?

Fundus, body, atrum (continuous with duodenum in small intestine)

What curves does the stomach have?

Greater and lesser curvature

Greater- on outside, lesser- on inside

What is the greater omentum?

Structure that hangs off greater curvature of stomach

Apron-like in structure, protects abdominal viscera

What is the histology of the stomach?

Mucosa, submucosa, muscularis externa, serosa/adventitia

What is the mucosa of the stomach?

Folded into ridges and folds- rugae

* Folds extend into lamina propria

Simple columnar epithelium

Secretes mucus- protects stomach from acids secreted by gastric glands

What are rugae?

Allow stomach to expand following ingestion

What is the submucosa of the stomach?

Contains blood vessels, lymphatics, glands, nerves plexuses- supply stomach tissue with oxygen

What is the muscularis externa of the stomach?

Has 3 layers of smooth muscle arranged in different directions-outer longitudinal, middle circular, inner oblique

What is the serosa/adventitia of stomach?

Stomach is covered by serosa

What is the small intestine?

6 metres in length

3 portions

Attached posterior to abdominal wall

What are the sections of the small intestine?

Duodenum, jejenum, illeum

What is the duodenum?

25 cm

C-shapes, encloses head of pancreas

What is the jejenum?

2\.5 m

In upper left quadrant of abdomen

What is the illeum?

3\.5 m

In right lower quadrant of abdomen

What is the histology of the small intestine?

Mucosa

Submucosa

Muscularis externa

Serosa

What is the mucosa of the small intestine?

Has vili- finger like projections extending into lumen

Simple columnar epithelium with many absorptive cells

Brush border- increases surface area for absorption

Enteroendocrine cells- secrete hormones involved in regulation of satiety, blood sugar level, growth of epithelial cells

Lamina propria- forms core of each villus, has blood capillaries, lymphatic capillaries- collections of lymphatic tissue in here- Peyer’s patches

Intestinal glands- crypts of Lieberkun- deep folds of mucosa, secrete intestinal juices

Plicae circulares- permanent transverse folds that help increase surface area for absorption

What is the submucosa of the small intestine?

Submucosa of duodenum-has duodenal glands- secretes alkaline mucus- protects small intestine

* Glands not found in jejenum or illeum

What is the muscularis externa of the small intestine?

Has 2 smooth muscle layers

Nerve plexus is located between 2 layers of muscle

What is the serosa of the small intestine?

Outermost layer of small intestine= serosa

What is the large intestine?

Terminal portion of digestive tract

3 sections- cecum, colon, rectum- extends from small intestine to anal canal

What is the cecum?

First portion of large intestine

Extension off of it= vermiform appendix

What is the colon?

Second portion of large intestine

4 sections

What are the four sections of the colon? (in order)

Ascending colon

Transverse colon

Descending colon

Sigmoid colon

What is the transverse colon?

Below liver, crosses abdomen to join descending colon below spleen

What is the descending colon?

extends down abdomen from splenic end of transverse colon to sigmoid colon

What is the sigmoid colon?

S-shaped terminal portion of colon that leads into rectum