lab practical 2

**Eyelid/palpebrae**

covers eye

**Medial/lateral commissure (canthus)**

medial and lateral junctions of upper and lower eyelids

lacrimal carnucle

located on the medial commissure – produces oily secretion

conjuntiva

inner surface of eyelid; secretes mucus

Lacrimal Apparatus

ecretes tears (contains lysozyme – an antibacterial enzyme). Apparatus consists of:


1. Lacrimal gland – located superior and lateral to each eye
2. Lacrimal canaliculus – tears enter thru lacrimal punctum
3. Lacrimal sac
4. Nasolacrimal duct

Ciliary glands

modified sweat glands found between eyelashes; lubricates eye

Tarsal glands

sebaceous glands posterior to eyelashes; produces oily secretion, lubricates eye

six extrinsic eye muscles

* **Lateral/External rectus**
* **Medial/Internal rectus**
* **Superior rectus**
* **Inferior rectus**
* **Inferior oblique**
* **Superior oblique** 

Fibrous layer

outer connective tissue layer.

Consists of:


1. Sclera: “white of the eye”
2. Cornea: transparent anterior structure for light entry

Vascular layer (Uvea)

middle layer; iris - most anterior part.

Consists of:


1. Ciliary body: found anteriorly; composed of ciliary muscle (controls lens shape) & ciliary processes (secretes aqueous humor).
2. Choroid: found posteriorly; blood-rich nutritive layer containing dark pigments preventing light scattering

Sensory layer

innermost layer, contains the two-layered retina. The retina consists of:


1. Pigmented epithelial layer: layer closest to choroid layer; covers ciliary body & posterior side of iris
2. Neural (nervous) layer: transparent layer containing photoreceptors (rods & cones); extends up to ciliary body
Rods: for black and white vision; used in dim light
Cones: for color vision; used in bright light; concentrated at the macula lutea (its center is the fovea centralis)
Blind spot located at optic disc where optic nerves leave the eye

Ciliary Zonule

AKA: **Suspensory ligament.** Holds lens vertical; ciliary muscle contraction changes lens thickness to focus light onto retina

Lens

found anteriorly; focuses light onto retina.

Divides eye into two segments:


1. **Anterior segment/cavity**: contain watery aqueous humor (formed by ciliary body; reabsorbed by scleral venous sinus). Has 2 chambers:
Anterior chamber (before iris); Posterior chamber (after iris)
2. **Posterior segment/cavity**: contain gel-like vitreous humor

Cones

photoreceptor in retinal layer that perceives color light; bright light; found mostly in **fovea centralis**

Rods

photoreceptor in retinal layer that perceives black/white; dim light; found mostly in periphery

bipolar cells

connects and modulates input from photoreceptors to ganglion cells. In the retinal layer.

ganglion cells

 project axons to the brain via optic nerve and tract.  Ganglion cell axons leave the eye thru the **optic disc**. In the retinal layer.

Visual pathway to the brain

Light stimulus causes impulses to travel from the: Optic nerves ⇒ optic chiasma (some optic nerves cross to opposite side) ⇒ optic tracts ⇒ superior colliculus & lateral geniculate body of the thalamus ⇒ occipital lobe (visual cortex)

emmetropic eye

normal eye; focuses properly.All images are inverted by the lens when focused onto the retina

myopia

near-sightedness; image focused in front of retina

hyperopia

far-sightedness; image focused behind of retina; **presbyopia** – far-sightedness caused by age-related decrease in lens elasticity

Astigmatism

irregular corneal curvatures that distort image

Auricle/pinna

composed of skin covered cartilage

external acoustic meatus

 external auditory canal lined with ceruminous glands (secretes wax)

Tympanic Membrane

eardrum that vibrates with same frequency as sound waves that enter canal

middle ear

consists of a tympanic cavity containing auditory ossicles

auditory ossicle

Malleus, Incus, Stapes

Amplify and transmit tympanic membrane vibrations to **oval window** (on **cochlea)**

Pharyngotympanic/auditory tube

Connects the tympanic cavity to nasopharynx. Equalizes middle ear pressure with outside air

Inner ear

\-consists of a system of bony (osseous) labyrinth filled with the aqueous fluid perilymph; bony labyrinth subdivided into:


1. Cochlea: involved in hearing
2. Vestibule: involved in equilibrium
3. Semicircular canals: involved in equilibrium

\-Suspended inside the perilymph of the bony labyrinth is the membranous labyrinth which consists of the cochlea, vestibule, and semicircular canals (the inside of the membranous labyrinth is filled with the more viscous endolymph)

Cochlear duct (scala media)

filled with endolymph; separates cochlear cavity into upper chamber (**scala vestibuli**) & lower chamber (**scala tympani**).

scala vestibuli

terminates at **oval window** with stapes, filled with perilymph

scala tympani

terminates at **round window**; filled with perilymph

spiral organ

found within cochlear duct; contains the sensory receptors (hair cells that project to **cochlear nerve**, part of **vestibulocochlear nerve C.N. VIII**).

Membrane of Spiral Organ: Basilar membrane

 forms the floor of cochlear duct where hair cells rest

Membrane of Spiral Organ: Tectorial membrane

contains a gelatinous membrane that **stereocilia** from hair cells project into

Membrane of Spinal Organ: Vestibular membrane

roof of cochlear duct

Sound Transduction – how sound is converted to nerve impulses

The stapes sends vibrations through perilymph of the scala vestibuli and scala tympani.  These vibrations cause the basilar membrane to move and thus stimulate the hair cells there (sensitivity to specific sound frequencies depends on hair cell location):

* __High frequency__ sounds detected primarily by hair cells at the __base__ of cochlear duct
* __Low frequency__ sounds detected primarily by hair cells at the __apex__ of cochlear duct

weber test

determines if sound conduction  is equally loud for both ears.  If not, may indicate sensorineural deafness from side with less sound.

Rinne test

compares conduction between bone and air.  If air conduction sounds lower, can be caused by compared earwax, a perforated eardrum, inflammation of the middle ear (**otitis media**), or damage to the ossicles.

Vestibular apparatus

suspended in perilymph Vestibule (monitors static equilibrium): composed of:


1. Utricle: detects horizontal acceleration
2. Saccule: detects vertical acceleration

Semicircular Canals

* contains the membranous **semicircular ducts**; monitors angular acceleration (dynamic equilibrium)
* Three ducts: anterior, posterior, and lateral.
* filled with endolymph

Vestibule

the utricle and saccule contain hair cells that project **stereocilia** and **kinocilium** into the **otolithic membrane** – gelatinous material containing **calcium carbonate** crystals called **otolith**.  Movement of the head causes the otolithic membrane to move and stimulate or inhibit the hair cells to alter electrical signals sent along the **vestibular nerve** to the brain.  

semicircular canals

contain hair cells in the **crista ampullaris** (sensory area) of the **ampulla**.  The stereocilia of the hair cells in the crista ampullaris are covered by a gelatinous cap (the **ampullary cupula**) that moves when you move (when you move, the endolymph ‘pushes’ against the cupula).  As the cupula moves, the hair cells send movement information to the brain as electrical impulses through the **vestibular nerve**.

neurons

nerve cells that function to transmit electrical impulses

neuroglia

cells that support the neurons

Soma

the neuron’s cell body (a cluster of cell bodies in the PNS is known as a __ganglion__ while in the CNS it is a __nucleus__)

Axon Hillock

tapered structure between soma and axon (important for producing the action potential)

Dendrites

processes that conduct electrical impulses towards the soma (usually receives a signal from another cell)

Axon

process that conduct electrical impulses away from the soma (in the CNS, a bundle of these processes form __tracts__, in the PNS, these axon bundles form __nerves__)

Axon/synaptic terminal

found at the end of axon.

Synaptic cleft

gap found between the axon terminal of one neuron and the target cell

Oligodendrocytes

* produce myelin
* located in the CNS

Schawwn Cells

* produce myelin
* Located in the PNS

Neuroglia

* are important to neuron function. 
* They can:
* Produce myelin to insulate a neuron’s axon
* Form __nodes of Ranvier__ found between myelinated sections of the axon.  These nodes help propagate and increase action potential velocity

How does an electrical impulse (action potential) travel down the neuron?

* An action potential is formed at the axon hillock when:
* An excitatory stimulus reaches axon hillock.  This causes
* Influx of Na+ ions into the neuron which depolarizes the membrane at that area (makes that area more positive) 
* When the depolarization reaches a **threshold** level, more Na+ ions enter the cell at that area
* Further membrane depolarization (influx of more Na+) occurs so the charge inside the cell actually becomes positive (normally at rest, the inside of a neuron is negatively charged)
* Na+ influx stops when the cell becomes positively charged (at \~ +30 mV) at that area.  K+ ions then start leaving the cell.  This repolarizes the cell at that area (starts turning the inside charge back to negative state).
* Once the cell is repolarized at that area, K+ ions stop leaving and the resting potential (the cell’s negative membrane potential) is restored.

absolute refractory period

* immediately follows an action potential – further stimulation cannot generate another AP

relative refractory period

* follows absolute refractory period – a strong stimulation can cause the generation of another AP

olfactory sensory receptors

bipolar neurons; extend cilia out from epithelium into mucus layer to detect odors, axons extend thru cribriform plate, form nerves, & synapse at olfactory bulb.  From there, impulses bypass the thalamus and go directly to the olfactory area of cortex.

tongue

covered by 3 types of papillae containing taste buds


1. __Foliate__ – located on the side walls of posterior tongue
2. __Fungiform__ – mushroom-shaped papillae located on the superior surface
3. __Vallate__ – arranged in a V formation on posterior surface

Taste buds

composed of a globular arrangement of:

* __Gustatory epithelial cells__ – the receptor cell responsible for taste sensation, developed from support cells
* __Basal epithelial cells__ – stem cells that develop into support cells

Impulses carried to sensory cortex by facial VII (anterior 2/3 of tongue), glossopharyngeal IX (posterior 1/3 of tongue), & vagus X (pharyngeal area)

taste receptors

opening that exposes taste cell microvilli (gustatory hairs) to oral cavity

gustatory cell

(from the gustatory epithelial cell) contact with certain chemicals causing the gustatory receptor cell to depolarize

Endocrine System

helps nervous system coordinate/integrate body activity by releasing hormones (steroids, peptides, & amino acids) into the circulation system

* A specific hormone affects only its target organs (organs that have receptors for that hormone)

Pituitary gland

attached to hypothalamus through the __infundibulum__ (stalk); has two functional lobes

Anterior Pituitary

* (adenohypophysis) releases hormones to the body through the __hypophyseal portal system__ (primary and secondary capillary beds and the __hypophyseal portal veins__); **6 hormones secreted**:
* __Follicle-stimulating hormone (FSH)__: gonadotropin regulating gonad gamete production/hormone activity
* __Luteinizing hormone (LH)__: gonadotropin regulating gonad gamete production/hormone activity
* __Adrenocorticotropic hormone (ACTH)__: regulates adrenal cortex activity
* Thyroid-stimulating hormone (TSH): regulates activity of thyroid gland
* Growth hormone (GH): regulates body/muscle/bone growth \*\*(too little GH causes dwarfism; too much GH causes gigantism)
* Prolactin (PRL): regulates breast development/lactation in females

posterior pituitary

(neurohypophysis) releases:

* Oxytocin: stimulates uterine contractions (birth & coitus) & milk ejection in lactation
* Antidiuretic hormone (ADH): stimulates kidney collecting tubules to reabsorb water from urinary filtrate & increase blood pressure via vaso-constriction of arterioles \*\*(too little ADH causes diabetes insipidus)

Pineal Gland

located on roof of 3rd ventricle in brain, produces:

* Melatonin: involved in biological rhythms.  May have an inhibitory effect on reproductive system (prevents precocious sexual maturation)

Thyroid gland

located in throat, secretes:

* Thyroid hormone (TH): controls body metabolism & cellular oxidation; two active hormones:
* T4 (thyroxine) 
* T3 (triiodothyronine) 
* Calcitonin: increases calcium deposit in bones; decreases blood calcium levels

Parathyroid gland

located on posterior surface of thyroid, secretes:

* Parathyroid hormone (PTH): releases calcium from bones to increase blood calcium, stimulates kidneys to activate vitamin D and reabsorb more calcium from filtrate \*\*(too little PTH causes __tetany__ – prolonged muscle spasms)

Thymus

located behind the sternum & above the heart, produces:

* Thymulin, thymosins, and thymopoietins: responsible for maturation/specialization of T lymphocytes used in the immune response

Adenal glands

located on kidneys

* Adrenal medulla controlled by sympathetic system to release:
* Epinephrine (80%)
* Norepinephrine (20%)

adrenal cortex

releases corticosteroids:

* Mineralocorticoids (aldosterone): regulate sodium reabsorption in kidney tubule 
* Glucocorticoids (cortisone, hydrocortisone, corticosterone): increase blood glucose to resist stress
* Gonadocorticoids (androgens, estrogens): sex hormones \*\*(too much gonadocorticoids cause hirsutism & masculinization)

Pancreas

located behind stomach, produces digestive enzymes & both insulin and glucagon

* Insulin: decreases blood glucose levels \*\*(too little insulin causes __diabetes mellitus__; too much insulin causes __hypoglycemia__)
* Glucagon: increases blood glucose levels

Gonads

reproductive organs (ovaries and testes)

* Ovaries: located in pelvic cavity, produces:
* Estrogens: stimulates development of secondary sex characteristics, regulates menstrual cycle (uterine lining) & mammary glands for lactation
* Progesterone: regulates menstrual cycle, uterine musculature in pregnancy & mammary glands for lactation
* Testes: located in scrotum, produces:
* Testosterone: stimulates development of secondary sex characteristics, maturation of reproductive organs, & responsible for sex drive

Blood

connective tissue that has non-living fluid matrix (plasma) that suspends living cells (formed elements)

Formed elements

* 45% of whole blood
* __Erythrocytes__: red blood cells (RBC) – most; transports oxygen
* __Leukocytes__: white blood cells (WBC) – immune system
* Platelets: blood clotting

Plasma

* 55% of blood
* Over 90% water
* Contains nutrients, gases, hormones, wastes, metabolites, proteins, electrolytes 

Erythrocytes

anucleated (lacks a nucleus) red blood cells (RBC’s); concave shape; unable to replicate/repair themselves; lasts 100-120 days

Leukocytes

white blood cells (WBC’s); nucleated cells produced from hemocytoblast stem cells in bone marrow; can move into/out of blood vessels (this process is known as __diapedesis__); has amoeboid motion; two main groups:

* __Granulocytes__: cytoplasmic granules stain differentially with Wright’s stain
* __Neutrophil__: most abundant of WBCs – active phagocyte (engulfs foreign particles), number increases with infection
* __Eosinophil__: attacks parasitic worms, lessens allergic reactions
* __Basophil__: contain granules with histamine, causes the inflammatory response
* __Agranulocytes/agranular leukocytes__: no visible cytoplasmic granules; found more in lymphatic system 
* __Lymphocyte__: smallest leukocyte; functions in immunological response; two types:
* __B lymphocytes__: produces blood antibodies
* __T lymphocytes__: has ‘antibodies’ on cell surface to detect and destroys grafts, tumors, & virus-infected cells
* __Monocyte__: largest leukocyte, converts to macrophages when inside tissues; act as macrophages (engulfs foreign particles)

Platelets

cell fragments of megakaryocytes in bone marrow; vital role in blood clotting

Coagulation

injured tissues release tissue factor TF while platelets release platelet factor PF3 ⇒ 

  they combine to form __prothrombin activator__ ⇒ 

  converts __prothrombin__ (in blood plasma) to __thrombin__ ⇒

  polymerizes soluble __fibrinogen__ (in plasma) to insoluble 

  __fibrin__ which forms the clot

Blood typing

* RBC contain surface __antigens/agglutinogens__ which are determined by genetics (inherited).  Blood contains antibodies/agglutinins that reacts with RBC that contain other antigens on their cell surface (your blood should not contain antibodies to the antigen on your red blood cell)
* Blood types: A, B, AB, O
* Rh: also known as the D antigen. (+ indicates the presence of the antigen, - indicates its absence) 

Type AB

contains antigens A and B

Type B

contains B antigens

Type A

contains A antigens

Type O

contains no antigen

Leukocytosis

Abnormally high WBC count indicates bacterial/viral infection

Leukopenia

Decreased WBC count indicates typhoid fever, measles, infectious hepatitis, cirrhosis, TB, excessive antibiotic/X-ray therapy

Leukemia

uncontrolled proliferation of WBC & reduction of RBC & platelets

Polycythemia

Increased RBC count from living in high altitudes or bone marrow cancer (tumors causing growth of RBCs)

Anemia

Decreased RBC count. Types of anemia:

* __Iron deficiency__ – caused by lack of iron
* __Sickle cell__ – RBC have abnormal shape causing decreased O2 carrying ability
* __Aplastic__ – bone marrow produces too few RBC’s
* __Pernicious__ – reduced RBC production due to lack of vitamin B12

Hematocrit

the percentage of blood volume occupied by RBC’s; PCV (packed cell volume) – used to detect anemia – high PCV to hemoglobin ratio indicates anemia

erythropoietin

hormone from kidneys that stimulate RBC production in bone marrow

Erythrocyte Sedimentation Rate (ESR)

measures RBC settling.  

* Low sedimentation: normal person
* Increase sedimentation: person with increased production of fibrinogen & immunoglobulins

Hemoglobin determination

measures Hb concentration in RBCs. 

* Normal person: 12-18 grams/100ml of blood
* Anemic person: lower value than normal
* Polycythemia: higher value than normal

blood typing

RBCs have antigens on cell surface.  Antibodies against these antigens can be used to determine blood type.  

* For example:  if a RBC has the A antigen on its cell surface, then exposing the blood to A antibodies will cause the blood to coagulate (the antibody will attach to its antigen).

heart

part of the cardiovascular system; the myocardium is composed of cardiac muscle; reinforced by dense fibrous connective tissue network; base of the heart is found beneath 2nd rib, apex at the left on top of the diaphragm

Pericardium

* (doubled walled fibroserous sac), serous fluid lubricates heart, prevents friction
* __Visceral pericardium/epicardium__: inner layer - closest to muscle; from the base of the heart to the apex.  At the apex, it forms the __parietal pericardium__ which attaches heart to diaphragm
* __Fibrous pericardium__: outer layer; formed from dense connective tissue; lined by parietal pericardium.  \*\*__Pericarditis__: pericardial inflammation due to serous pericardial layers adhesion 

cardiac muscle cells

 line the myocardium

* Are striated muscle cells that have only one nucleus
* Have branched endings.  The ends of the cardiac muscle cells are attached to other cardiac muscle cells by **intercalated discs**:
* Contains **gap junctions** that link the cytoplasm of one cardiac muscle cell to the adjacent cardiac muscle cell.  Allows ions and small molecules to flow from one cell to another – allows for action potential to travel through the myocardium

Interventricular septum

separates left & right atria and ventricles, respectively.