Organelles and cell function Flashcards
1
Q
4 Types of organic molecules
A
- Carbs - Glycogen is a polysacharide
- Proteins
- Lipids
- Nuclei Acid
2
Q
Carbohydrates
Function
Organisation
Example:
A
- Main source of Energy
- Mono, Di, Polyscaharides
- Glucose / Sucrose / Glycogen
Dehydration Sythesis forms bonds between sugars
3
Q
Proteins(Amino acids)
Function
Organisation
Example:
A
- Major componet of most Tissues
- • Primary: Amino acid sequence • Secondary: Conformation (Alpha helices, B-sheets) • Tertiary: Folding to shapes (Ionic bonds) • Quaternary: 2 or more subunits
- Heamoglobin (Quaternary)
4
Q
Lipids (Glycerol and fatty acids)
Function
Organisation
Example
A
- Cell Membranes / Energy reserves
- • Fatty Acids – Energy (glycerol backbone and hydrocarbon chain) • Phospholipids/Glycolipids – Cell membrane bilayer, hydrophobic= fluid and impermeable to polar substances (charged polar head, glycerol backbone, fatty acid chain) • Steroids – Hormones (4 bonded C rings)
- Fatty Acid→Triacylglycerol Phospholipids→Phosphatidylcholine Steroid→testosterone
5
Q
Nucleic Acid (Nucleotides)
Function
Organisation
Example
A
- Carry genetic info
- • DNA Adenine←→Thymine Guanine←→ Cytosine • RNA Uracil instead of Thymine
- DNA RNA
6
Q
Glycocalyx
A
Carb enriched coating covering outside of eukaryote cells
Found on apical portion of microvilli (BRUSH BORDER) in digestive tract
7
Q
Cells
Charactaristics
A
All living things composed of cells
Basic structural and fuctional unit of life
All cells from pre-existing cells
Red blood cells only cells without nucleus
8
Q
Cell membrane Functions
A
- Respond to stimuli via receptors
- Fluid Mosaic model of plasma membrane – Phospholipid bilayer – Made of phosphatidylcholine – Can fuse with other membranes – No movement of anything large or polar across membrane (except lipids) – Membrane proteins travel throughout surface
9
Q
Cell membrane proteins:
A
Integral Proteins - Penetrate bi-layer or not completely
Peripheral Proteins - Inside or Outside cell
Lipid anchored proteins
10
Q
Passive transport through Cell Membrane
A
Passive
Diffusion: High to low con gradient ( Non polar O2 / Co2)
↑speed = ↑ Temperature, ↑ energy state (gass), ↓ size, ↑ conc. gradient
Osmosis: H2o From high to low concentration (Hyper/Hypo/Iso)
Facilitated Diffusion: Much faster than simple diffusion Requires a membrane-bound carrier/ Reaches endpoint
Aqauporins: Integral proteins allow passive movement of water even through it is polar
Filtration: Only in the Kidney tubeoles
11
Q
Active transport through cell membrane
A
Requires energy / against gradient /includes pumps / carrier proteins
PRIMARY
Maintains specific gradient ↑NA+ outside, ↑K+ intside – uses energy from ATP and Phosphorylation
SECONDARY
Energy stored in electrochemical gradient of another solute (usually sodium/potassium) – uses NA/K pump to go against gradient
12
Q
Endocytosis
Pinocytosis
Phagocytosis
A
Pinocytosis: extracellular fluids, solutes Receptors not required
Endocytosis: requires membrane receptor to bind & internalize
Phagocytosis: Large molecules and foreign particles
13
Q
Cytoskeleton function (4)
A
- Structure and Support
- Intracellular transport
- Contractility and Motility
- Spatial Organization
14
Q
Microtubules
A
Size 24nm
Protein: TUBULIN
Hollow structure / MAP hold mictrotubles in place
15
Q
Types of Microbubules
A
- Axonal transport: highway that motor proteins carry organelles on
- Cilia: Help transport fluid and materials / 9 - 2 cofiguration
- Basilar body Anchor cilia / 9 triples config
- Centrioles : Appear at poles during mitosis, attach to mitotic spindle separating DNA into daughter cells 9 triples config
16
Q
Microfilaments + function
A
6nm
Protein: ACTIN
Functions: Wound healing
movement of axons
vesicles
phagocytosis
cytokinesis
17
Q
Intermediate filaments
A
10nm
Most stable
Provide shape and structure to cell
Protein (various)
Cytokeratin - Epithelium
18
Q
Rough Endoplasmic Reticulum
A
Synthesis/processing of secretory proteins
Continuous with nuclear envelope
Labyrinth of flattened sacs
Ribosomes on outside (Rough appearance)
19
Q
Golgi Apparatus
A
Modifications of secretory proteins
• Adding sugars, folding etc.
− Stacks of flattened disklike membranous cisternae
− Usually less than 8 in a stack
− Vesicles bud from sides
20
Q
Smooth endoplasmic Reticulum
A
Synthesis of lipids
o Liver: detoxification of drugs, toxins
o Liver: Release of glucose from glycogen when required
o Muscle cells: sequestering of Ca and regulated release
- Most remain membrane bound
- more “tubular” than the rough ER
- some like hormones secreted
21
Q
Lysosomes
A
Fuses with vacuoles for digestion of cellular organelles, bacteria, macromolecules
− membrane-bound bags of enzymes
− Peroxisomes (special type) destroy peroxides
22
Q
Nucleus
A
Contains genetic information (DNA)
− Pores in envelope allow for mRNA and protein movement
− Usually 1 per cell but some special cells can have 2
− Easiest structure to see under microscope
23
Q
Nucleolus
rNA synthesis
(2 types of chromatin)
A
- Heterochromatin: (Inactive, clumps)
- Euchromatin: (dispersed) Active in RNA synthesis
24
Q
Mitochondria
A
Energy production through cellular respiration
− 1 glucose = 36 ATP − Glycolysis (anaerobic) in cytoplasm, 2 pyruvic acid into mitochondria →2 ATP
− Oxidative phosphorylation in mitochondria matrix →34 ATP
25
Dimensions of the Eye
Globe diameter: **24-25 mm** (1 inch)
Lens: **10mm x 4mm**
Iris: **12 mm** (wide) x **11 mm** (tall) **37 mm** circumference
26
Differentiate right vs left fundus images:
- side optic disc is on is which eye it is (right side right eye, left side left eye)
- optic disc is nasal to macula -blood vessels make L shape on left eye
27
Vitriad - -
Sclerad - -
**Positioning Vocab:**
**Vitriad**-closer to vitreous, more interior
**Sclerad**- closer to sclera, more exterior
28
Caruncle
**Vascular nodule of modified skin** (has hairs and accessory lacrimal glands)
29
Plica seminularis
“half moon” at nasal canthus allows eye to move the center of vision without stretching anything
30
Eyelids (Palpabrae)
+ FNX
**Tarsal portion**: part that closes over eye
**Orbital portion**: between brow and tarsal portion
Upper lid moves more than lower, on closing
**Functions:**
* covers globe when closed
* Protection
* Moves tears toward drainage
* Blinking spreads tear film over cornea
* Structures to produce tear film
31
Punctum
(2Puncta)
* Hole
* First part of tear drainage
* upper and lower
32
**Meibomian Glands**
Oil glands in lid margin that can be seen with the naked eye
Located at the posterior aspect of tarsal plate
33
Cilia
Eyelid Margin
**Cilia** eyelashes
**Eyelid Margin**: tissue between cilia and meibomian gland
34
Palpabral Fissure
Palpabral Sulci / Sulcus
**Sulci** “groove or fold” in the lid
**Palpebral Fissure**: opening
35
Canthi (plural of canthus):
x2
**Lateral canthus:** 5-7 mm medial to bony orbit
Lies on globe
**Medial Canthus**: Sit on medial margin of bone
Separated from globe by “Lacrimal Lake”
*Lacrimal Lake: x triangular space at the medial angle of the eye, where the tears collect*
36
Canaliculi (plural of canaliculus):
“tiny canal”
Upper and lower
Sits near medial canthus
Drain tears
37
Lacrimal glands
**secretes** portion of tear film
only superior
38
Extraocular Muscles
Name location
**6 skeletal muscles**
Meet at common tendinous ring before socket ends
**Rectus “straight”** Superior, inferior, lateral, medial
**Oblique** :Superior, inferior o Trochlea- “pully” for superior oblique
39
Chambers of the eye + Volume
**Anterior chamber (200 µ)**
Cornea= anterior boundary iris=posterior boundary
**Posterior chamber (50 µl)**
Posterior border=lens & zonules anterior border=iris
**Vitreous Chamber (4.4 ml)**
Contains vitreous that maintains eye shape
40
Fluids of the eye + Function
**Aqueous**
Function: nourishes + removes waste from lens + cornea (avascular) Maintains IOP (continuous production)
**Vitreous**
* Transparent viscoelastic gel: 2/3 eye volume
* 98% water
* refractive index **1.33**
* sodium hyaluronate + collagen II makes it jelly/viscous
41
Describe the flow of Aqueous Homour
**Flow:**
Produced by **Ciliary processes**
percolates between **ant. Lens and post. Iris**
into **anterior chamber**
exits through t**rabecular meshwork** in anterior angle
through **canal of schlem** into **aqueous vein**
42
Eye comprises of 3 TUNICS
+
Structures includes in each
**Fibrous**
Outermost , **Cornea sclera** with **limbus** as transion zone
**Vascular**
middle layer, highly vascularised **Iris, cilliary body, Choroid**
**Neural**
Inner layer **RPE**
**\**Ora Serrata*** *Transition point for vascular and neural tunic Oral bay (give scalloped look) Dentate process (space in-between bays)*
43
Functions of Cornea and Sclera
**Cornea:** (Transparent)
* Main refracting structure (80%)
* Protection
* Tear film
**Sclera:** Opaque
* Protection
* Withstand forces
* Imparts shape/size to eye
44
Iris
**Colored part of eye**
**Pupil:** opening in iris that allow light in
**Collarette**: physical structure on iris that separates Pupillary region and Ciliary region
**Pupillary Margin**/Ruff/Ring: highly pigmented, medial most aspect of iris
45
Ciliary Body
**Pars plana**: ciliary ring thin/flat but wider
**Pars plicata**: ciliary processes finger like projections thick but narrower
**Ciliary Muscle**: contract as part of accommodation
46
Ora Serata
**ciliary body -------- choroid Transition Zone**
**Ora Serrata** Transition point for vascular and neural tunic Oral bay (give scalloped look) Dentate process (space in-between bays)
47
Choroid + Functions
1. Blood supply to outer retina appear to glow orange on retinal imaging (retinal blood vessels supply inner retina)
2. Thermoregulation by inc./dec. blood flow
3. Pigment absorbs light prevents reflect back through retina o Can affect IOP Due to blood flow regulation
4. Possible role in eye growth regulation? By secretions
5. Possible function as another means of accommodation? by thickening
48
Retina + Defined structures part of neural Tunic
Neuroretina: **senses light and creates electrical impulses**
**Macula**: center of retina o Fovea: area of highest acuity in center of macula
**Optic nerve:** transfers visual information from the retina to the brain **Optic disc:** point of exit ganglion cell axons that form the optic nerve and point of entry for major blood vessels (central retinal artery + vein)
49
**Crystalline Lens:**
**Zonular fibers:**
**Crystalline Lens:**
_Focuses light on retina_ Connected to uveal tract by zonules
**Zonular fibers:** (Insert between ciliary processes)
Insert on anterior and posterior lens
**Accommodation:** Ciliary muscle contraction releases tension Increases curvature / Increases dioptric power
50
Epithelium to functional units
Requires **membrane specializations**
Lining tissue can line either a lumen (space) or the outside world **(APICAL**) aspect
Cells are closely bound into a functional unit
Function: move molecules and fluids, secret and absorb substance
51
Apical Spesializations of Epithelial cells
1. **Glycocalyx:** proteins, sugars, lipids on plasma membrane
2. **Microvilli** folds to increase surface area histological term = **brush boarder**
3. **Junctional complexes**
52
**Tight junction**/Occluding Junctions (zonula occludens)
in Epithelial cells
Most apical
**Proteins encircle cell perimeter on apical surface**
*Strands of globular proteins Proteins: **occludin and claudin** − both always present − Impermeability of skin epidermis due to claudin (Defect in gene would cause dehydration & death) − Maintains the blood-brain barrier − Certain signals open the junctions*
* Plasma membranes of 2 neighboring cells stitched together
* **Stop** molecule **movement along paracellular pathway**
* Permeability depends on amount of proteins in a strand
53
Adhering junction (zonula adherens)
in Epithelium
Less tight, **transmembrane proteins** connect neighboring cells
* “**belt” structure** encircles cell inside membrane • Proteins: **Cadherins** and catenins
* − Catenins: transmembrane dimer
* − Cadherins: intercellular with 3 subunits
* − bind to actin cytoskeleton
* Calcium dependent linkages
* **Connects external environment to cytoskeleton** (domains in both)
* Signal transmission from outside to inside
54
Desmosomes (macula (spot) adherens)
in Epithelium
Found in tissues subject to **mechanical stress** (Cardiac muscle, skin epithelium) o Gives strength and rigidity
* “**Spot”** links to **intermediate filaments** (tonofilaments made in skin and epithelium)
* **Transmembrane protein linkers** make dense plaques
* Denser plaques on inside anchor to intermediate filaments as dark plaque • P**rotein: Cadherin**s
* − Different domain structure from those of belt adherens
* − Dimer protein with 2 subunits
55
Hemidesmosomes
in Epithelium
**Lateral basement membrane**
Integrins link plaque **to keratin intermediate filaments**
_connect BM to underlying tissue_
**anchor basal domain to basal lamina**
56
Gap junctions
in epithelium
**Intercellular channels act as molecular pipelines between cells**
• Integral protein: **connexin** (make connexons) **Hydrophilic channel** in the center forms path between cells
− **6 subunits**
− Allows passage of water, and small ions and molecules
– Metabolites, coenzymes, amino acids
– Cardiac muscle electrical impulse from SA node
– Certain areas of brain have these, don’t require transmitters
57
Basement Membrane
in Epithelium
**Extracellular to the epithelium** BASAL aspect (between epitheliums and connective tissue) **synthesized and secreted by the epithelium**
58
Classification of Epithelial _layer_ TYPE
(3)
* **Simple:** one cell layer thick
* **Stratified:** more than one layer
**• Pseudostratified:** (pseudo-fake) appears stratified, but all cells touch the basement membrane (only location we need to know is **trachea)**
59
Classification by Epithelial cell shape (5)
* **Squamous:** thin, fish-scale shaped
* **Cuboidal**: square
* **Columnar**: rectangular (higher than wider)
* **Transitional:** basal layers cuboidal or columnar, *surface layers often squamous (in renal system, don’t need to ID because it looks different if bladder is full or not)*
60
Simple SQUAMOUS Epithelium
Simple Squamous Epithelium _skinny_ and _appear irregular in en face view_
\*\*need to ID is cross sectional view
**Endothelium** Special term for squamous epithelium lining in blood vessels and cornea
**Mesothelium** Lines all cavities of the body
61
Stratified Sqaumous Epithelium (Non-keratinized)
**Stratified Squamous epithelium (non-keratinized)**
* _non-keratinized_ = all cells are **living** (retain nuclei)
* j_unctional complexes_ on _lateral surface_s connecting cells
* **cuboid** on basement membrane and then become thinner and transition to **squamous at apical level**
* **Lines wet cavities Mouth, esophagus, vagina**
62
Corneal Epithelium
Layers and Function
**5-7 layers** of cells
**Stratified, non- keratinized**
Apical and basal only 1 cell layer Layers:
* **Basal cells (1 layer of columnar/cuboid cells)**
Sit on basement membrane, attached to Bowmans
Mitosis (stem cells) in limbus region
* **Wing cells (2-3 layers)**
Middle layer synthesizes and stores keratin tonofilaments
**• Superficial cells (2-3 layers)**
_Barrier_ between _tear film and inner cornea_
In constant state of degeneration, slough off
_Dense microvilli and glycocalyx have enzymes that interact with tear film_
Junctional complexes prevent movement of water
63
Corneal Abrasion
**Abrasion:** quick to cover BM (6mm lesion closed in 48 hrs.)
1. Cessation of mitosis
2. Cells at edge retract, thicken, lose attachment to BM
3. Cells enlarge, migrate to cover defect
4. Mitosis resumes be able to ID layers ithelium b I a Stroma endothelium hexagonal shape
NORMAL
**Constant mitosis** and regeneration of cells **7d turnover time**
Cells divide in limbal basal cell layer
New cells move **centripetally (to center)** and **superficially**
Sluff off after lifespan
64
Bowmans Layer
Special basement membrane
− 1 layer synthesized by overlaying epithelium like normal basement membranes
Basal Lamina: _(Lamina lucida and lamina densa): made of collagen_
* **No regeneration of Bowmans if damaged (scar will form)**
* Cells adhere via **hemidesmosomes**
* Collagen passes t**hru Bowmans to stroma**
65
Endothelium
**Simple Squamou**s
**Hexagonal mosaic**
* secreted by endothelium
* Lateral surfaces joined by junctional complexes
* **Large # mitochondria**
* active in pumping fluid
* Low regenerative capacity
Poly morphism / Megathism
3500/mm2 to 2500mm/2
66
Corneal Endothelium functions
**Functions:** − **Na-K ATPase** in basolateral membrane
**Maintains hydration** dt Constant evaporation
**Prevents excessive hydration** (pumps H2O out, too much water = opacity)
Barrier to pathogens
67
Decement's Membrane
* **Secreted by endothelium**
* Increases in thickness throughout life (3x as think by age 50)
* Thicker in periphery o Ends at Schwalbe’ s line internal landmark of limbus thicker collagen
* **No hemidesmosomes** connect to endothelium! (different than epithelium)
* **Regenerates** if damaged o Continuously secreted for replacement
68
Simple Cuboidal Epithelium (Polygonal)
## Footnote
**Retinal Pigment Epithelium (RPE)**
69
Retinal pigment Epithelium - Simple Cuboidal
Define cell structures
* **Apical microvilli** (outer retina faces apical RPE)
* **Lysosomes and phagosomes** (degradation of photopigment material that is constantly regenerated)
* Nuclei line up
* Lots of **mitochondria, rER and Golgi because lots of proteins are made**
* **Melanin** absorbs excess light and UV radiation
In **light adapted** eye, moves **into microvilli** and protect outer segments of retina
In **dark adapted** eye, moves **from microvilli back into the cel**l
70
Bruch’s membrane = basement membrane
Synthesized by cells making choriocapillaris
o Outer collagenous zone
o Elastic layer
o Inner collagenous zone
71
Structure features of the RPE
72
Simple Columner Epithelium
+
Example of where
I**ntestinal lining Medullary collecting ducts**
**+**
**Conjuctiva (But stratified 2 layers)**
73
Conjunctival epithelial cells
**Stratified columnar & cuboid** ONLY 2 LAYERS (usually)!
Goblet cells secret mucin layer of tear film
Conjunctiva of eye
**bulbar conjunctiva over sclera fornix transition point palpebral conjunctiva**
74
How does epithelium change folowing the lids. Fron the skin of the lid to the cornea
Stratified Squamous Keratinized on skin of lids
→ Stratified columnar & cuboid on Conj (bulbar and palp.)
→ Simple Squamous on cornea Stratified squamous (lid margin) to str. columnar Palpebral Conjunctiva
75
Transitional Epithelium
Where and shape
Only found in the Urinary tract
Dome shaped apical cells.
76
Non-Ocular locations of Epithelium Types
**Pseudostratified Ciliated Columnear Cells**
Have Cillia & Goblet cells
On fase very irregular
**TRACHEA**
77
Non-Ocular locations of Epithelium Types
**Simple columnar Epithelium**
**Intestinal lining / GI tract**
Medullary collecting ducts
78
Non-Ocular locations of Epithelium Types
**Transitional Epithelium:**
Only located in **renal system** Appear hen when **bladder is full**
79
Glandular Epithelium
Endo & Exocrine differences
• **Exocrine glands**: secrete product into a duct system to go to target • **Endocrine glands**: Ductless. Secrete product into capillary network
\*\*\*ALL EXOCRINE GLANDS _*SECRATORY EPITHELIUM\*\*\**_
80
Exocrine glands Structural classification
* **Secretory:**
* o acinar (round)
* o tubular (oval)
* o coiled
* **Duct:**
* o simple (unbranched)
* o compound (branched)
81
Functional classification of exocrine Glands
**Merocrine**
**Merocrine:**
o **release by exocytosis**
o secretory vesicles that fuse with plasma membrane
o protein products
**o Most common**
82
Functional classification of exocrine Glands
Holocrine
**Holocrine:**
## Footnote
o discharge **entire breakdown of secretory cell**
o sebaceous **(oil) glands**
83
Functional classification of exocrine Glands
**Apocrine**
Apocrine:
o discharge of **membrane-bound vesicles**
o some **sweat glands o very rare**
84
Identify Type and Location
**Simple Unbranched Tubular:**
o Entire intestine
o Goblet cells
o Secretes into lumen
85
Identify Type and Location
**Compound Tubuloacinar**
**Sublingual, submandibular & lacrimal gland** (main and accessory)
o Both tubular and round secretory portion
o Lacrimal gland : forms water (aqueous) part of tear film,
86
Lacrimal system
Label
Lacrimal structures important
87
Identify the structures of the lacrimal system
88
What glands are in the eyelids
What type of secretion
**Meibomian glands:**
* Oil
* Along lid margin
* Delays tear film evaporation Lubricates and protects cornea **Glands of Zeis:**
* Oil gland
* Attached to lash follicles
**Glands of Moll**:
* Special sweat gland
* Apocrine glands at lid margin
89
Accessory lacrimal glands
**Same product and complex branched structure as main lacrimal gland**
**− Glands of Krause:** o Fornix of conjunctiva
**− Gland of Wolfring:** o Above tarsal plate
90
Characteristics of connective tissue
Supporting Tissue
cells that **live** in an **extracellular matrix** not closely bound
Vascular (except cartilage)
**Support, protection, binding, fat storage**
**Immune functions** (“wandering” WBCs) Plasma calls, B lymphocytes, neutrophils, eosinophils, macrophages,
91
Components Of connective tissue:
3 Big groups
## Footnote
**Cells**
**Ground Substance**
**Fibers**
92
**Cell** components of **Connective Tissue**
Fibroblasts - Most common
Adipocytes
White (Wandering cells) RBC's
Chondrocytes (cartilage)
Osteocytes / -blasts / -Clasts
93
Ground Substance in Connective tissue
GEL that withstands Stress
Composed of: – **GAGs** + proteins = **Proteoglycans**
– Extracellular fluid and ions Proteoglycan aggregates:
– **Glycosaminoglycans** (GAGs) Highly neg. charged, large, **hydrophilic** Link to proteins to form **Proteoglycan**
94
Fibers of connective tissue
**Collagen:** Main fiber
* most abundant protein
* Tensile strength
**Elastic fibers:**
* Elastic fibers=elastin protein
* Fibers or sheets (elastin)
* Give skin + vessels stretch and elastic recoil GAGS thin dark thicker lighter
**Reticulin,** l*aminin, fibrillin: o Small fibers o Delicate support framework for organs o Collagen III*
95
**Collagen** Structure in Connective tissue
Pimary structure: **amino acid sequence**
− Secondary: **3 helixes wrapped around each othe**r
− Secreted as T**ropocollagen**
− Stacked in specific staggered array **forming banded structure**
96
Collagen types
* **Collagen I** (90%)– Skin, bone, tendon, ligaments, **sclera, corneal stroma**
* **Collagen II** – Hyaline and elastic cartilage, **vitreous**
* **Collagen III** – Organs, smooth muscle, **reticular lamina of BM** – scaffolding giving structural support to _basement membrane of epithelial tissue_
* **Collagen IV** – **Basal lamina of epithelium** (**basement membrane component)** – Non-fibrillar
97
Specialized Connective tissue
Elastic Fibers
Reticular Fibers
Cross-linking of mature elastic fibers enable stretching and recoil
• Fibers stain black or dark blue
**Reticular** (Reticulin)- Secreted by reticular tissue in liver hepatocytes
• Very thin, branching
98
**Simplist Connective tissue**
Dense Regular connective tissue
?structures of the eye
Tendons and ligaments
SCLERA
CORNEAL STROMA
_Fx Tensile strength and resistance to forces_
99
Corneal Stroma
Tissue / Fx ? / Properties
**Dense regular connective tissue**
Cells are **keratocytes** (fibroblasts)
Fx: keeps IOP stable, resist force
48 D refractive power
**Transparent** due to size and **arrangement of collagen fibers,** smoothness of covering epithelium (5-7 layers) and being avascular **Avascular unlike other connective** tissue o flatter in periphery o **Collagen Type I,** V and VI
100
Basement Membrane and Bowmans Layer(Made by overlaying epithelium)
Tissue type?
Dense regular connective tissue
**Basement membrane: Type IV collagen,** laminin, fibronectin, perlecan
**Bowmans layer** beneathe it**; only in primates**
**Collagen fibrils (type I)**
Cells adhere via **hemidesmosomes** link to anchoring filaments of **collagen VII** squish nuclei linedup of o **pass thru Bowmans into stroma** Penetrate and branch among collagen fibers
101
Why is the cornea transparent?
Each layer called a lamella Collagen fibrils Embedded in **proteoglycans that act as spacers** arranged **90-degree** angles (At **limbus** run c**ircularly to maintain curvature)**
Fibroblasts join one another connected by gap junctions Regular arrangement and **spacing essential to maintenance of transparency**
102
Sclera
## Footnote
**Type** of connective tissue and properties
**Dense regular connective tissue**
Posterior to choroid
**Fibroblasts** in ECM of collagen, **elastin**, PGs (not spacers in this tissue)
Structural integrity of eye (**maintain size and shape)**
70% water − **Opaque due to water content** higher than cornea
**Avascular** exept *for superficial scleral vessels*
103
Weakest part of sclera?
Lamina cribosa
## Footnote
− Scleral collagen fibers that cross where optic nerve leaves the eye − Weakest point
104
Dense **Irregular** connective tissue
Less dense
fewer collagen fibers **Found in dermis of skin**
Cell type of Epithelium above Dermis:
**Keritinized stratified Sqaumous Epithelium**
105
Loose (Areolar) Connective tissue
Found in **IRIS STROMA**
**G**I tract , Respitory, Urinary,
Surrounds vessels, nerves, and glands
Fx: Support, Elastisity
immune
106
ADIPOSE Tissue
Fx , Characteristics
Stores fat: energy, thermoregulation, cushioning, receptors hormones (insulin)
* fat droplets push **nuclei to the side**
* Vascular
* 2 types: o **White (in adults)**
o brown (only found in fetus, infant and hibernating animals)
107
Vitreous Chamber
**Transparent Viscoelastic gel**
– **98% wate**r
* Refractive **index 1.33**
* Cells: **hyalocytes**
* **Collagen II and hyaluronic acid** main molecules that make it gel •
108
Vritreous Chamber
Name 4 Attachment sites
o Edge of disk
o Retinal attachment
Peripappillary attachment
Hyaloideo-capsular ligament (weigert)
109
Functions of the Skin (Integument)
**Functions:**
* • Protection
* • regulation of temperature
* • excretion
* • synthesis vitamin D in sunlight
* • Reception of pain, pressure, temperature
110
Epidermis - Type of tissue
Dermis - Type of tissue
Epidermis = **stratified squamous keratinized epithelium**, provide water proofing, specialty cell location
Dermis = **dense irregular connective tissue**, (excepts around receptors, glans and BVs→ loose areolar) location of smooth muscle attachments, blood supply and hair follicles
111
Thick VS Thin Skin
**Thick:** •Palms and soles
**•5 layers**
•No hair, no oil glands **Stratum Lucidum thicker**
MANY layers of epidermis, tighter packed
**Thin**: •Rest of body
* **Thin stratum corneum**
* 4 layers **FEW wispy layers of keratinized (dead)** cells at the top
112
Identify the layer SC
**Stratum corneum**
**Flattened dead keratinocytes** provide water proofing (prevent dehydration)
**Deeper layers,** **desmosomes** intact
Upper layers, not intact = “**desquamation**”, call sluff off
113
Identify layer SL
**Stratum Lucidum**
Clear and thin
Larger in thick skin Protective shield
114
Identify Layer SG
**Stratum Granulosum**
2-4 cell layers thick
**Keratohyaline granules**
Stage in keratinization as cells move up to top layer (life of a cell basal to top is ~1 month)
115
Identify Layer SS
**Stratum spinosum**
**Junctional complexes** hold calls together
T**onofilaments**, spines
**desmosomes**= “prickle cells” **appear spiked** and connect 1 cell to another
Tight binds make it r**esistant to abrasion**
116
Identify Layer SB
**Stratum basale** (germinativum)
Mitosis (germinating layer)
**Single layer Cuboid or low columnar keratinocytes** **Hemidesmosomes** connect it to the **BM**
Many desmosomes bind adjacent cells
117
**Melanocytes** , Specialized functions
Melanocytes:
synthesize and secrete **melanin tyrosinase** + **melanin = melanosome** (mature melanin)
cytoplasmic extensions of melanocyte cells r**each up into str. Spinosum** and **establish contact with keratinocytes**,
**granules** containing **melanin pinch off**, phagocytized by cells and form **protective barrier around nucleus**
118
Melanin In Skin
types and what determines skin colour?
**Degraded** more **rapidly by lysosomes in white skin**:
color **NOT form # of melanin**, only **due to degradation rate,** production the same Types of melanin
**Eumelanin** → brown/black
**Pheomelanin** → reddish yellow
**Albinism:** no pigment, genetic defect, lacking enzyme **(tyrosinase) to make mature melanin**
119
Papilae and Receptors in DERMIS
**Papillae:** Invagination of dermis into epidermis
Contain **BVs and receptors**
− special receptors in papilla: **Meissner’s Corpuscle** → **fine touch receptors, low frequency stimuli**
− **free nerve endings**: t**emp and pain receptors**
− **Pacinian Corpuscles**: Large collagen capsules surrounded by fluid with axon receptor
inside (look like onion) →**Deep pressure/ vibration**
120
Identify the Structures and function
Cell type: **secretory epithelium**
**Sebaceous Gland(oil)**
• **Holocrine glands** - Type
• Bag of cells
• **attached to hair follicle**
**Sudoriferous Gland(sweat):**
• **Simple coiled tubular** - type
• in Dermis + hypodermis
• Glands: simple cuboid epithelium
• Duct: stratified cuboid etothelium
121
Blood supply to skin
**NO BVs in epidermis**
**Dermis:** BV’s branch → cutaneous plexus subpapillary plexus→ loops of capillaries, sphincter to close off and regulate body temp Hypodermis: large BVs →Subcutaneous plexus
122
Eyelids
Skin / Tissue / Glands
Transition of tissue types: **Lid skin** (strat. squ. ker. ep.)→ **Conj** (strat. Cub/col ep.)→
**cornea** → (strat. sq. non ker. ep.)
0.5 mm thinnest skin in body
**Protection, moves tears to drainage, spread tear film, Contains glands**
Tarsal (**Meibomian) glands:** oil ducts lead upper **lid 30-40 vs 20-30 in lower**
**Glands of Moll**: sweat at edge of lid
**Glands of Zeis**: eyelash follicle oil gland
123
Identify Structure and Cell type
**Conjunctiva**
**Mucin-secreting columnar epithelium**
White goblet cells **Inner eyelid (palpebral conj.)**
**Globe (bulbar conj.)** Continuous w/ corneal epithelium
124
Clinical considerations for SKIN
cancers
**Freckles**
• Hyperpigmentation in spots (more melanin)
**Basal cell carcinoma**
• tumors in stratum basale cells
• usually due to excessive sun exposure
• Not usually malignant
**Squamous cell carcinoma**
• Keratinocytes in spinosum
• May metastasize (break through basement membrane)
**Melanoma**
• Melanocyte cancer
• Frequently breaks free and gets into blood/lymph system and spreads
125
Lens charactaristics
**Thick**ens over time from ~3.5 to 5 mm (n**ormal adult male 4 mm**)
**Diameter**: 6.5-9 mm (infant to teen) (**normal adult male 10 mm**)
Cells = “fibers” not really fibers (also falsely named in muscle “fibers”)
**Alters refractive index by ~15-20 D**
Changes **shape during accommodation**
Behind iris, medial to ciliary body
**Transparent
Avascular**
Continues to grow throughout life 3.5 to 5 mm
126
Lens Capsule
**Capsule**
* • Transparent envelope
* • Encircles entire lens
* • **produced by cuboidal epithelium at poles**
* • Basement membrane
**Anterior is thicker**, **mitosis continues** so it continues to thicken with age
• Posterior is thinner and size is stable
• thinnest at poles
Has **elastic properties**
• **Collagen fibers** • **Insertion of zonules** at “zonular lamella”
127
Lens Modified epiithelium
**Epithelium + Fibers**
**• Germinative zone →active mitosis**
• Synthesizes and secretes capsule
• **Cuboid only on anterior surface** → become c**olumnar by equator**
• **Terminates at lens bow** (c shaped nuclei of new fibers)
New cells more equatorially → **elongate into fibers** and f**orm sutures**
• **Nuclei** move **anteriorly as they age**, and **oldest cells become anuclear** (no more mitosis)
• **Central nucleus = harder material**
• Fibers have hexagonal shape and are filled with crystalin
• High refractive index
128
**Embryonic Lens Development**
1. • Starts as a **hallow ball of epithelial cells** with open center called lens cavity
2. • Primary lens fibers (oldest fibers) **elongate and take over the cavity**
3. • These fibers form the **embryonic nucleus**
4. • **Secondary lens fibers** elongate **anteriorly and posteriorly** and meet neighbors from the other side **to form anterior sutures**
5. • **Primary fibers detach** from the posterior basement membrane and **nuclei degenerate**
6. • Because of this there are **no longer any epithelial cells** on **posterior side** to form capsule
129
Lens Divisions (Parts of the lens like onion)
Certer of lens ?
**Embryonic nucleus:**
made by p**rimary lens fibers**
**Highest refractive index**
**Oldest proteins in the body**
NB
All others are made by mitosis of secondary lens fibers at equator
130
Lens Divisions (Parts of the lens like onion)
2nd and 3rd 4th layer from center of lens ?
**1)Fetal nucleus:** Remember **E** comes before **F**
## Footnote
laid down **before birth**
**2)Adult Nucleus**
birth to sexual maturation
**3)Cortex**
after sexual maturity
Lowest refractive index
131
Lens sutures
GZ - germinal transision zone
* **Lens fibers meet other fibers at poles**
* **Anterior suture** – Overlapping **apical aspects**
* **Posterior suture** –Overlapping **basal**
* During development meet in **3 branches**
* **Eventually become too large to meet** and sutures become more **complex pattern**
132
Identify structures
Image taken of posterior aspect of lens
133
Identify
Features of Zonular fibers
**Zonules of Zinn (suspensory ligaments)**
• Delicate **protein similar to elastin**
– Attach **2mm anterior** and **1mm posterior - Arise from pars plana**
– Fan out in V shape when they attach
**• synthesized by epithelium in pars plana**
– Blend with basal lamina of lens capsule
134
3 Types of zonules
Function and where they attach
3 types of zonules
* *Primary:** attach **to lens**
* *Tension Zonules:** anchor to **basement membrane of ciliary muscle**
* *Secondary:** connect a few primary together and **attach to Tension Zonules**
135
Identify the structure formed in the diagram
**Canal of Cloquet:**
fluid filled pipe
**hyaloid artery that is needed in development** for nutrients
breaks down
**leaves collagen wall**
136
What does Aging and UV do to the lens
• **Cataract formation from UV irradiation**
– Lens absorbs all **UV (300-400 nm)**
– Lens **epithelium damage**
– Lens fibers: degradation, **modification of crystallins**
– Usually senile but can also be congenital, traumatic, toxic, disease-related
**• Lens grows through life**
– Increase curvature
– Lens center moves slightly forward into anterior chamber
– **Presbyopia (inability to accommodate) from loss of elasticity**
137
Identify Structures Lettered
TM - trabicular Meshwork
PC - Posterior Chamber
C - Cornea
CP - Cilliary Process
AC - Anterior Chamber
CM - Cilliary Muscle
LZ - Lens Zonule
PM - Pupil Margin / Rough
138
Identify the structures
139
Anterior iris Structures
+ epithelial changes
**Epithelial bilayer** continuous over **iris and ciliary body**
Pupillary margin/rough is continuation of bilayer I**n iris both layers are pigmented**, on ciliary processes the **posterior layer becomes nonpigmented** and **anterior stays pigmented**
Lens has **pupillary region** that sits **on lens** and **root** at **angle Thinnest in the center and thicker at pupillary region and root**
The anterior portion of iris less pigmented in lighter colored eyes
**Collarette** separates **ciliary zone and pupillary zone of iris**
140
4 Layers of the IRIS
**1) Anterior border**
* Denser CT than underlying stroma
* **Dense fibroblasts with holes** between them called **“crypts of Fuchs”** that a**queous flow**s through
* **Melanocytes underneath**
* **Collagen**
**•2) Stroma**
* o **Loose CT w/ fibroblasts, melanocytes, collagen**
* o Very **vascular**
* o **Fluid movement** in and out of stroma **through crypts**
* o Mast cells, macrophages (“clump cells”)
* o Sphincter smooth muscle 1 mm width
141
4 layers of IRIS
Bottom 2 (Specialized Epithelium)
**3-4 Bilayer Epithelium**
o **Anterior layer:**
o **basilar processes, myoepithelium** = **pupillary dilator muscle**
**o Posterior layer:**
o more **cuboidal, pigmented epithelium,** junctional complexes between cells
o **ridges (folds and furrows)**
2 layers sit apex to apex
142
The Ciliary Body
• **5-6 mm** (width) ring **from scleral spur** (ant) to **ora serrata** (post)
• **Anterior pars plicata**
• 2 mm wide; **70 radial folds = ciliary processes**
o Minor ones interspersed with major ones
• **Posterior pars plana**
o 4 mm stretch to ora serrata (limit of retina)
• Lined by bilayer ciliary epithelium – Bilayer continuous with iris epithelium
o Inner non-pigmented; outer pigmented
o Inner: aqueous, zonules, vitreous
143
Identify structures and cell in diagram.
144
Histological divisions
**Epithelium** of Ciliary Body
**\*\*Cells sit apex to apex**
**Posterior layer nonpigmented**
Zonules
Pars plicata 70-80 processes
Pars plana: thin bilayer epithelium
145
Ciliary Muscle fibers
**Ciliary Muscle**
* Circular fibers
* Radial fibers
* Longitudinal fibers
Each layer defined by their orientation
146
Identify these structures and cell types
147
Anterior + Posterior Chamber
FLOW of Aqeous
Anterior Chamber
– **Cornea and anterior surface of iris and lens**
– Lateral recess is **iridocorneal angle w/trabecular mesh**
– **250 μl** aqueous humor
**TRONSPORT Metabolites** to lens and cornea; production **of IOP**
Posterior Chamber
– **Bound by lens & zonules, Iris**
– **Production of aqueous**
148
Traditional Aqueous flow:
* *Ciliary processes** → between posterior iris and anterior lens→ into **anterior chambe**r→ into
* *angle** →through **trabecular meshwork** → o**ut canal of Schlemm**
149
Why Glaucoma?
Glaucoma
Pathological **change in trabecular mesh work** and **Schlemms canal** Resistance to IOP increases Can be congenital or from angle close when the angle is physically blocke
150
Cartilage
Function and Properties
**Function:**
* Special connective tissue
* semi-rigid support
* _template for bony skeleton_
**Properties:**
**Only avascular connective tissue** (nutrients must diffuse through matrix)
Only cell in all types → ***chondrocytes***
Therefore, different properties of each type **depend on matrix components**
151
Type of Tissue
Cells and metabolism
**Cartilage**
**Cells surrounded** by **matrix they secrete**
Cells live in l**acunae** (Hollow cavity)
**Limited mitosis** ( Unable to regenerate)
**Cells contain:**
Lipids
Glycogen
Lots of RER and Golgi (to constantly secret matrix)
Surrounded by perichondrium
152
**Identify**
TYPE
Location Function
**Hyaline Cartilage** (Most Common)
• Fetus skeleton template • **Adult articular surfaces of joints**
• **Respiratory tract**
(Tracheal rings, Bronchi, Larynx,Nose)
• costal (rib) cartilage
* **Enables movement of bones with synovial fluid**
* Support and framework for airways
153
Features of Hyaline Cartilage
• **Type II collagen**
• resilience • pliability • fibrous
• **cells bunched** together in **isogenous groups**
• **lipid droplets in cells**
• surrounded by **vascular adipose
tissue** (blood supply for cartilage)
154
**Identify**
TYPE
Locations and function
**Elastic Cartilage**
* External ear • Auditory canal • Epiglottis
* **Prevents food in airway**
* **Support and framework of ear**
155
Elastic Cartilage
Features
• **Type II collagen**
• resilience
• **pliability**
• elasticity
NB • **elastic fibers and sheets** (purple or black
stain)
• **cells bunched together in isogenous groups**
• **lipid droplets in cells**
156
Fibro Cartilage
(Lacks perichondrium)
• Intervertebral discs • Symphysis pubis • Mandible • Joint capsules • Menisci and tendon attachments
**Functions** • Cushions spine. • Joint movements
• Skeletal system connections
mainly type II collage, some type I • **_Lacks Perichondrium_** • Small chondrocytes in clusters • Less rigid matrix • Minimal PGs and water • Lots of matrix
157
Growth of Cartilage
2 types
Growth:
**Appositional (early)**
Developing cells in the perichondrium (chondroblasts/fibroblasts) lay down matrix at surface
**Interstitial (later)**
Mature cells divide and remain in the same lacuna (form isogenous group)
Cells secret territorial matrix and push away from one another
158
Diagnosis for calcification of cartilage and process
**Arthritis:**
calcification of **articular cartilage**
Repair by **perichondrium is limited, c**ells only add matrix
If **blood vessels grow** → i**ncrease in oxygen** → **CaPO4** crystals form in **matrix** (**calcification**) → cartilage **becomes bone** → tissue
immobile
- **Hyaline cartilage most prone to calcification**
- Increases with aging
- Can be genetic
159
Features / Charactaristices of
**BONE Tissue**
Bone has **inorganic components** - Inorganic salts (Ca+ PO4 hydroxyapatite)
Makes it dense and brittle
**Vascular**
Bone comp : Type I collagen 90% + Proteoglycans + Ground substance
FX: Support - **Storage and release of Ca+ and PO 4** ions
**Blood cell formation (hematopoiesis)**
160
Types of **Lamellar** Bone
identify
***Woven** - featus and bone repair*
Parts of Lamellar Bone:
– Compact (outside)
– Cancellous/spongy (interior)
Trabeculae (spiky structure that makes up meshwork of spongy bone)
161
Histology of Bone:
* *Osteons/ Haversian systems:**
- **Functional uni**t of compact bone
- Gives very **regulated organization**
- Concentric **arrays of lamellae with osteocytes (mature cells) in lacuna between them**
- **Haversian**/Central **Canal**: at **center**, bring **BVs, nerves and lymphatics** to bone
- **Canaliculi:** **radiate from lacuna and connect cells to outside osteons**
* *- Volkmann’s**/Perforating Canal: **connect central canals of different osteons**
162
Identify the cells
**Osteocytes:**
**Mature cells in lacunae**
Trapped in the matrix they synthesize and secrete
Live in **lacunae (fluid filled spaces)**
**Long processes** in canaliculi that connect neighboring cells
**Gap junctions** at contact points of processes (share waste, nutrients, oxygen between cells)
Minimal protein synthesis (low energy required, **small amount of RER, condensed
heterochromatin)**
163
Identify the cell Marked and its functions
**Osteoblasts**: **B**lasts **B**uild
* **Large cells** on s**urface** of developing bone
* Cuboid or polygonal
* Lays down osteoid (nonmineralized organic matrix)
* Polarized
* Can revert to osteoprogenitors or become osteocytes if enzymes are released and mineralize matrix, trapping cells
164
Identify and describe function
**Multinucleated** Lie in depressions (Howship’s lacunae/ruffled border)
**Osteoclasts: Clasts** Crush
**Resorbtion** (digestion) and **remodeling**
Dissolve **mineral** with **organic acids**
Dissolve **organic matrix with lysosomes**
Lysosomes from golgi release enzymes & H+
Causes **CaPO4** to **break down**
Products transferred to blood
* *Regulation:**
* *Parathormone** ***increases blood Ca***→stimulates **resorbtion** and **delays mineralization**
* *Calcitonin** ***decreases blood Ca***→inhibits **resorbtion**
* *sealing zone stops** from digesting the wrong part
165
Which hormones are responsible for Bone remodeling
in OSTEOCLASTS
**Regulation:**
Parathormone **increases blood Ca**→stimulates resorbtion and delays mineralization
Calcitonin **decreases blood Ca**→inhibits resorbtion
sealing zone stops from digesting the wrong part
166
Identify the structures of a single Osteon
167
Blood
Function:
Tissue Type?
**Special connective tissue**
Functions:
**Transport** of gasses, nutrients, waste, hormones (mainly oxygen and carbon dioxide)
**Body temperature regulation:** sphincter muscles control blood brough to the surface of skin
168
Composition of Blood
**Extracellular matrix** (liquid cells are suspended in)
− **Plasma: 55% total volume**
• Water
• protein (fibrogens, albumen, globulins)
• solutes (ions)
**Cells (formed elements)**
45 % total vol.
**− Red Blood Cells (erythrocytes)**
**− White Blood Cells (leukocytes)**
**• *Granulocytes***
o Neutrophils, basophils, eosinophils
**• *Agranulocytes***
o Lymphocytes, Monocytes
**− Platelets (thrombocytes**)
169
Hematocrit
\<35 Ameamia
Hematocrit: %RBCs/volume
Serum w/o fibrinogen = **plasma**
## Footnote
When centrifuged you can see blood is:
**35-55% RBCs (packs to bottom)**
**1% WBC’s and platelets (Buffy coat)**
**44-64% plasma**
170
**Proteins** in Plasma
* *Fibrinogens:**
* *Largest** − Synthesized in liver when needed
Usually soluble − *insoluble to form clots in wounds*
**Albumins:**
Smallest − Colloid osmotic pressure
− *Bind insoluble metabolites as transport protein*
− *Makes blood same tonicity as extracellular matrix*
**Globulins**
*− Antibodies*
− Involved in immune response
171
RBC's
**Erythrocytes**
**Oxygenated in lungs (Bright red color)
Deoxygenated in tissue capillaries (Dark red)**
* Transports **O2 for delivery**, **CO2 for remova**l
* Only **anucleate cell** in humans
* No organelles / **Biconcave disc / most** abundant element.
* Smallest cell in the body (7-8 μm x 2.6 μm) • **Elastic**
* Aged ones destroyed in liver, spleen, marrow
• Contains **hemoglobin** = **Quaternary structure**
o 4 polypeptide chains w/ iron group (heme) in the center of each
o Each binds an O2 (RBS can carry 4 oxygen molecules)
172
**Diseases** Affecting RBC's
**o Sickle Cell Anemia:**
Caused by one **aa substitution in B chain**
Deoxygenated become insoluble in RBC making them inflexible and fragile
Blood is **more viscous**, and **RBCs get trapped in capillaries**
## Footnote
**o Thalassemia “anemias”:**
Defective **alpha or beta chains causes hemolysis of RBCs**
173
Platelets
Thrombocytes
Platelets (Not cells)
• **Derive from megakaryocytes in marrow**
• **Microtubules** and **microfilaments** give them **size and shape**
• 4 types of granules, 2 “true” (lysosomal and “very dense”)
## Footnote
Function:
• **Aggregate into clot** at vessel rupture
o **Release serotonin** (from dense core) = **vasoconstriction**
o Release **thromboplastin** = f**ibrin clot**
174
Disease Affecting
Thrombocytes
• Thrombocytopenia
o Reduced platelet #
o Spontaneous bleeding
o failure to clot/seal wounds
o **Can occur due to marrow suppression from chemotherapy**
175
Megakaryocytes
• Large
• Sit in **bone marrow**
• Polyploid
• Multilobed nucleus
• Extensive cytoplasm
Function:
• **Form platelets through disaggregating (breaking into small pieces)**
176
WBC's
Neutrophils
Neutrophils (Polymorphonucleocytes=PMNs):
• **10-12 μm; 60-70% WBCs**
• Lifespan of ~7 hrs
• Multilobular nucleus
**• Phagocytic**
– 2 types fine granules( Lysosomes + Azurophilic)
**Function:**
Responds to i**nflammation**
**1st line Defense against bacteria + fungus** - Ligands bind and bacteria recognized
- Can used cytoplasmic processes to bring bacteria closer to it - Phagocytizes and neutralizes - Apoptosis (dies)
177
Function of Neutrophils
178
WBC's
Basophils
o Small
o **Least common** in normal blood
o **Bilobed nucleus** difficult to see
o **Dark blue granules**
Function:
* *Allergic reactions**
- Vasodilation
- Inflammation
- Histamine
- Anaphylactic shock
- slow-reacting substance of anaphylaxis
179
Leukocytes = WBCs
**Granulocytes**– Contain primary and secondary granules
• Neutrophils, basophils, acidophils
* **Agranulocytes** – Contain only primary granules (smaller)
* Monocytes, lymphocytes
* All may leave bloodstream in response to stimulus – **“Diapedesis”**
180
Eosinophils/Acidophils:
## Footnote
• 12-15 μm, 3% WBCs
o Slightly larger than basophils
o **Bilobed nucleus (**easy to see)
o Numerous **large pink stained granules** (Peroxidase,histaminase)
Function:
Parasitic infections
- Phagocytic
- Limits inflammation
- Triggers asthma
- In gut mucosa / **In lamina propria – GALT**
181
Monocytes
o **Largest WBC**
o Large nucleus takes us ~1/2 cell
Function:
Macrophage
Phagocytosis of cells, debris, bacteria
- Chemotaxis calls to area needed
- In tissues, differentiate to:
**o Osteoclasts (bone)
o Kupffer cells (liver)**
o **Alveolar macrophages (lung)
o Langerhans cells (skin)**
182
Lymphocytes
o Quite prevalent
o Small about the same size as RBC
o Large round nucleus takes up most of the cell
* *o 2 types:**
- Small: **Tcells (Killer cells)** - Most common
- L**arge: Bcells** - Rarer
Function:
Immune responses
- recognize foreign Abs
183
Identify All the cells
184
3 types of muscle tissue
**Skeletal**
-Striated / Voluntary Control / Multinucleated
**Smooth (visceral)**
-Not striated, Involuntary, One nucleus
**Cardiac (Heart only)**
* -Striated, 1-2 Nuclei
* -Cells branch at end
* -Involuntary
185
Skeletal / Striated Muscle
o Striated (striped)
o **Voluntary control**
o **Multinucleated,** pushed to the **side of cell**
o **Uniform size** and r**ectangular shape but vary in length**
o Motor end plates synapse with motor axons
o Fine and “course” control
− depends on location
− Smaller number of cells controlled by 1 motor neuron=finer control
o **Post-mitotic**
− I**ncrease in size due to hypertrophy**
ex. going to the gym
Cell number stays the same, but cells get thicker
Increase in cell volume
Increase in # of proteins (myofibrils)
186
Striated Muscle cell structure
• Plasma membrane = **Sarcolemma**
– Nuclei beneathe membrane
• Specialized smooth ER = **sarcoplasmic reticulum,** surrounds myofibrils
– Reservoir and regulator of Ca++
**• Sarcoplasm** = cytoplasm
187
Structure of Skeletal muscle
**Sarco**- means muscle
**Sarcomere:**
functional unit of muscle
**I band:** only **actin,** no overlap
**H band:** only **myosin**, no overlap
**A band**: *end to end of myosin, overlap
Z Disk/Line: ends of sarcomere*
**M Line**: center **connecting myosin proteins**
Z disks move apart→ M and A stay the same size, H and I increase in size
188
Structural componets of Muscle fibers
Identify and describe
**Sarcolemma:**
plasma membrane
**Sarcoplasmic reticulum: (top label)**
specialized smooth ER
surrounds myofibrils
Next to T tubules
Reservoir of Ca+
**Sarcoplasm: Bottom label**
cytoplasm
Transverse tubules (T-tubules):
Indent into cell at A/I junction
2 per sarcomere
189
Identify the structure and describe
bundle of muscle cells
**Muscle fiber:**
cell (misnamed fiber)
**Myofibril:**
Many in each cell
**Myofilaments:**
Proteins
**Actin** (Smaller)
**Myosin** (Larger)
190
Sliding filament model of contraction
**Tropomyosin**: forms cross bridge with **head of myosin**
**Troponin:** connected to tropomyosin
o Action potential occurs
o Ca+ released from lumen of SR into cytoplasm of muscle cells
o Ca+ binds troponin
o Causes **conformational change of tropomyosin** to **unblock site on actin**
o **Myosin head binds actin**
o Change of **head from a 90 degre**e→ **more acute angle cases it to move actin forward**
o (Requires 3 ATP)
191
Muscle connective tissue components
**Epimysium:**
− Surrounds entire muscle
**Perimysium:**
− Thinner, more delicate
− Surrounds fascicles
− Contains vessels and nerves
**Endomysium:**
− Thick
− Collagenous fibers
− Wraps single muscle cell
− Brings in nerves and blood supply
192
Label and Identify
Label and Identify
193
Label and identify
EOM's
194
Smooth Muscle Locations
Locations
• **Vessels** (surround blood vessels)
• **Respiratory tract**
• Hollow organs (bladder, stomach)
• **_Iris sphinctor_**
• Ciliary body: ciliary muscle
## Footnote
• Arrector pili in skin. (Makes hairs stand up when cold)
195
Smooth Muscle in disease
**• Asthma**
– Constriction of bronchi
– Overactivity of smooth muscle cells
• **Smooth muscle retains mitotic ability**
**(Can form New cells)**
196
Cardiac Muscle tissue
**o Involuntary -** only in Heart
o 1-2 centrally located nuclei
o Cells **branch at end** + **Lots of CT** between cells
o **More extracellular matrix** between cells
o Vast blood supply
o **Gap junctions between cells**
− Contracts as a unit, ***“syncytium”***
o Has SER and T-tubule system similar to striated
o Huge mitochondria tremendous energy requirement
**o Post-mitotic**
o Intercalated disk − Zonula adherens anchors cells together
− Desmosomes give structural integrity
197
Cardiac Muscle disease
o Clinical correlations
− Heart attack
Cells die **Incapable of regenerating**
**Fibroblasts invade** and make scar tissue
Cells become **longer & larger and have to work harder**
198
The CHOROID
**• Posterior part of uvea**
• Thin, pigmented, vascular, conn tissue
– Nourishment, conduit to other parts of eye, light absorption
* From **optic nerve** margins **to ciliary body**
* 220 μm thickness in posterior, 100 μm anterior
• **Inner surface = part of Bruchs membrane**
• **Outer = suprachoroid**
– lamina fusca: outermost choroidal layer
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Functions of the choroid
* **Blood supply to outer retina**
* **Thermoregulation** by increasing and decreasing blood flow
* **Pigment can absorb light,** prevent reflect back through retina
* Choroid blood flow regulation can affect IOP
* **Resilient tissue**: **protects sclera from increases in IOP**
* Possible role in eye growth regulation
• Possible function **as another means of accommodation**
*o changing thickness by filling lacunae with fluid*
200
Choroid accomodation fnx
• Compensation to defocus:
o Hyperopic: choroid thickens, eye growth slows
o Myopic: choroid thins, eye growth increase
o First fond in chicks, in humans as well but much smaller changes
o Can be measured with an OCT in humans
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Structure of Choroid
* **Thin • Pigmented • vascular • connective tissue**
* Continuous with **anterior** parts of **uvea**
* From optic nerve margins to ciliary body
* **Thicker in posterior**, thins **anteriorly** as it reaches the **ora serrata**
* Separated from RPE by Bruch's membrane
* **Vortex vein**: large vein that drains choroid
202
Histological Layers
**• Bruch’smembrane**
**• Choriocapillaris**
**Stroma**
• Sattlers layer– Medium vessels
• Hallers layer – Large vessels
**• Suprachoroid**
**• Laminafusca**
203
Anterior Border (Vitread) of Choroid
**• Inner surface**
o outer most part of Bruch’s membrane is part of choroid
204
Choriocapillaris
(2nd layer of Choroid)
o Bed of **fenestrated capillaries**
o Density greatest near fovea
o **Extends to ora serrata**
o Is a **“vascular net”** with very regular structure
o Fed from **arterioles in Sattler’s layer**
Form hexagonal patches from one feeder
o Output through venioles
205
Stromal Layer of Choroid
* *o Sattler’s layer** - Medium vessels
* *o Haller’s layer** - Large vessels
− R**andom collagen I, elastic fibers, fibroblasts, melanocytes**
− Pigmentation greater in darker skinned people
**− Immune cells:** Mast, macrophages, lymphocytes
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**Suprachoroid**
**Lamina Fusca**
**• Suprachoroid**
o **outermost** choroidal layer
o transition zone
o fluid filled **AVASCULAR space between choroid and sclera**
o Continuous with supraciliary space of anterior eye
**• Lamina fusca**
o sometimes called its own layer but also can be used interchangeably with suprachoroid
207
LABEL
208
Label
209
Clinical inplications : Choroid
**Clinical Implications:**
Lipofuscin: lipid-rich waste
Builds up
Stops water movement
Forms barrier between Bruch’s and RPE
210
Blood circulation system
+
Exeptions
**• Veins:**
− bring blood toward the heart
**• Arteries:**
− bring blood away from the heart
**• Exception to rule:**
**− Portal systems**
− Vein or arteriole **interposed between 2 capillary networks**
− Occurs in the **liver, kidneys and endocrine system**
211
**Layers of Blood Vessels:**
Arteries and Veins similar excepts the walls of veins are thinner
212
Innermost layer of the bloodvessels
**Tunica Intima**
**• Endothelial cells:**
o **simple squamous cells** that line the lumen, **apical** on **lumen** side, basal forms BM
**• Subendothelial layer**
• Internal elastic lamina (IEL):
o **thicker and wavier in medium arteries**
213
Tunica Media
**Different in medium vs large arteries**
• **Circular Smooth muscle in medium/muscular** arteries
o l**ayers of muscle decrease** as arteries become small (single layer in smallest
arteriole)
• Sheets of **elastic and collagen in large/elastic** arteries
o acellular
• External elastic lamina (EEL) layer at edge
214
Tunica Aventitia
**Tunica Adventitia:**
* Loose connective tissue with fibroblasts
* Has its own blood and nerve supply
* **Thinner in large, thicker in medium**
215
Blood vessels
216
Microvascular bed
• Arterioles
• Capillaries
• **Postcapillary venules**
− Precapillary sphincter: shunts blood, **responds to local environment, “autoregulation”**
217
Capillaries
o Site exchange gas, fluid, ions, metabolites, wastes
o **RBC’s fold** to fit through smallest ones
o **single layer endothelium & basement membrane**
o 1-3 cells joined by t**ight junctions**
o Some w/ **specialized cells** that wrap around them: **pericytes**
218
Continuous capillary
* **Most predominant**
* Always have BM with tight junctions
* In CNS, muscle, lung, **retina, iris**
219
Fenestrated
cappilaries
* **Pores** bridged by diaphragm
* Molecules can **move through**
* Sometimes have a BM
* In endocrine, GI tract, kidney, **choroid**
220
Discontinuous Capillaries
• Rare
• **Huge holes**
**• Never have a BM**
• In liver, spleen, marrow
221
Blood Supply to the eye
Types of vessels Choroid
Layers of Choroid:
• Choriocapillaris:
o thin layer of capillaries closest to RPE
• Sattler’s:
o stromal layer with medium BV’s
• Haller’s:
o suprachoroid with large BV’s
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Vasculature of the eye
• The **capillaries** of the **iris** are **“continuous”**
o no leakage into stroma
• Endothelial cells joined by **continuous tight junctions**
o prevents blood-borne macromolecules from entering the iris stroma and the
aqueous humor
223
Blood vessels of the eye
**Pathology:**
− High cholesterol can cause fatty plaque deposits
− Lumen becomes more narrows
− Increased risk for clots
224
Nervous system cell types:
− **Neurons**→communicator cells
**− Glial Cells**→ support cells
225
Structure of a NEURON
**Axon:** electrical impulses travel down, only 1 per cell but can branch
**Terminal:** end of axon
\****Synapse** can occur on c**ell body, axon, spine** or **dendrite** of next cell*
\****post synaptic vs presynaptic is relative** to the other cells*
**Transmitter:** released at terminals to transmit chemical signal
**Dendrite:** site of contact from other cells
**Soma/Perikaryon:** special name for cell body of neuron
**Nucleus:** light stained nucleus with **dark stained nucleolus,** lots of euchromatin due to high
protein production
**Nissl Bodies**: special name for neuron **Rough ER,** site of protein production
**Myelin Sheathe:** made my **glial cells wrapping around axon** and squeezing out cytoplasm (lipid),
insulation/ saltatory conduction
**Nodes of Ranvier**: gaps in myelin (only in vertebrates), impulse jumps from node to node to
increase speed
**Neurofilaments:** special name for intermediate filaments of neuron
226
## Footnote
**Types of Neurons**
**• Motor**
o **largest neurons** with the largest cell bodies
o **motor end-plates** at neuromuscular junction
o any of 3 muscle types
o junctional folds increase surface area of receptor region
o synaptic cleft between terminal and junctional folds
**• Pyramidal Cell**
o **In cerebral cortex**
o Including visual cortex
o Triangular shape
**• Purkinje cells**
o In cerebellum
227
Types of Glial Cells
**PNS**
**Types of Glial Cells
PNS**
**• Schwann cells**
o Myelin
o Unmyelinated cells also associated with Schwann cells
o Wraps only 1 axon
**• Satellite cells**
o In ganglia
o Surrounds soma
o Local environment control
228
Cells of the **CNS**
**CNS**
**• Astrocytes**
o **Most numerous support cells** in brain
o **Fill spaces** between neurons
o Regulate extracellular matrix Protoplasmic astrocytes help blood brain barrier
o Contact Ependymal cells Line ventricles of CNS Cuboid epithelial cells
**• Oligodendrocytes**
o Myelin
o Not all axons are myelinated
o Wraps several axons
**Muller Cells
• Support cells in retina**
• Extend from one end of retina to the other
229
## Footnote
**Microglia**
**• Microglia**
o Phagocytes
o Cleans debris
o Helps with disease and injury repair
o Immune cells in brain and spinal cord
o **Migrate** to **sites of dead neurons**, proliferate and phagocytose
230
## Footnote
**Neurotransmitters**
**Neurotransmitters**
## Footnote
* **Exocytosis with vesicles**
* Most **binds a receptor**
* Lipid soluble (hormones) act on genes instead of receptor
* Open channels or activate second messenger
* Inhibit or excite action potential
* Enzymes destroy neurotransmitters left in cleft or reuptake system recycles
231
2 TYPES of neurotransmitter
**2 types**
o **Low molecular weight**
Synthesized in axon terminal
**Dopamine**
− Circadian rhythm daytime mediator in retina
**GABA**
− Inhibitory retinal transmitter
**Glutamate**
− Photoreceptor transmitter
**o Peptide (high MW)**
**Synthesized in cell body (soma)**
− VIP in retina amacrine and ganglion
− Glucagon in retina amacrines
232
Nicotinic Acetylcholine Receptors
• Nicotinic Acetylcholine Receptors
o Acetylcholine binds receptor
o Opens channel for sodium to flow through
o Flips membrane potential
o Causes calcium release in muscle cells
233
Nervous system
**Clinical corelations**
**• Multiple sclerosis**
− Demyelination of motor neurons in CNS
− replaced by fibrous tissue
− impulse conduction loss
− Limb weakness, swallowing & speech affected
**• Lateral sclerosis (ALS-Lou Gehrig’s)**
− Motor neuron degeneration in brain motor centers
− Limb weakness
**• Alzheimer’s (senile dementia)**
− Loss of neurons in cortex
− Protein “plaques” form outside neuro n
− tangles form in neurons
234
Spinal chord Sensory to Motor pathway
235
Protection of the CNS
**Brain and Spinal Chord**
**o Surrounded by protective CT (meninges)**
**− Dura**
• outer most layer
• Fibroelastic
• Tough dense CT
• Merges with periosteum
• Small subdural space underneath
**− Arachnoid**
• Fibrous
• Less dense
• Lined by simple squamous epithelium cells
• CSF and vessels in large subarachnoid space
**− Pia**
• Collagen, elastin, fibroblasts
• Very delicate
236
Blood Brain Barrier
**Blood-brain barrier**
o **Perivascular space i**n brain
o surrounded by basement membrane from **endothelium and end feet of glial cells**
o **Non-fenestrated endothelial cells** with **occluding junctions** prevent diffusion
from blood
o Glucose passes freeing but most others are blocked
237
NERVES
GREY Matter & WHITE Matter
**Nerves**
o **Afferent (sensory)**
**o Motor**
o Mixed
**Gray matter**
**o Neuron cell bodies**
o Central in spinal cord
o As spinal cord descends ratio of grey matter increases
o Outside in brain
**White matter**
**o Axons**
o Outside in spinal cord
o central in brain
238
PNS (Peripheral nervous system)
Connective tissue of nerves
**Peripheral Nervous System (PNS)**
**o Peripheral nerves**
o 31 spinal roots
**– 12 cranial nerves**
– Fascicles of axons
## Footnote
**o Connective Tissue**
**Endoneurium**
– Surround axons around myelin
**Perineurium**
– Surrounds fascicle of axons
**Epineurium**
– Surrounds nerves
– Thickest
239
Retina and Optic Nerve
* Extension of the brain
* Site of **phototransduction (PRs)**
* Local circuit processing
IMPULSE travel
• Ganglion cell axons to LGN(1st relay), to cortex
– EXIT at OPTIC DISC
240
Identify and explain cause
DRUSEN
## Footnote
**RPE digests old photopigment**.
If RPE can’t do this it dumps partially digested materials beneath RPE cells into or on Bruch's membrane
241
Identify the layers
242
Layers of the retina
* RPE
* **Photoreceptor**
* Outer limiting membrane
* Cell bodies rod and cones
* Outer plexiform
* Inner Nuclear
* Inner Plexiform
* Ganglion cell layer
* Optic nerve fibers
* Inner Limmeting membrane
**Photoreceptor Layer:**
− **Inner and oute**r segments **of rods and cones**
− Nuclei in cell bodies
− organelles in inner segments
− Disks in outer segments
− Cilia connect inner and outer segments
− project through fenestrated external limiting membrane into subretinal space
243
**Layers of the retina**
RPE
Photoreceptor
**Outer limiting membrane**
Cell bodies rod and cones
Outer plexiform
Inner Nuclear
Inner Plexiform
Ganglion cell layer
Optic nerve fibers
Inner Limmeting membrane
Synapse area made by **Mueller cells**
Contain **specialized structures** (synaptic ribbon and vesicles)
called the **Pedicle in cones**
o 2-3 indentations each holding the dendrite of **1 bipolar cell** and **2 horizontal cells**
called the **Spherule in rods**
o only 1 set of 1 bipolar and 2 horizontals are attached
244
**Layers of the retina**
RPE
Photoreceptor
Outer limiting membrane
**Cell bodies rod and cones**
Outer plexiform
Inner Nuclear
Inner Plexiform
Ganglion cell layer
Optic nerve fibers
Inner Limmeting membrane
**− Rods:**
smaller in enface view disks are separate/free-floating **density highest at 20 degrees from fovea −**
245
**Layers of the retina**
RPE
Photoreceptor
Outer limiting membrane
**Cell bodies rod and cones**
Outer plexiform
Inner Nuclear
Inner Plexiform
Ganglion cell layer
Optic nerve fibers
Inner Limmeting membrane
**− Cones:**
larger in enface view
disks are continuous invaginations not surrounded by plasma membrane
connected to one side
**density highest at fovea**
246
**Layers of the retina**
RPE
Photoreceptor
Outer limiting membrane
Cell bodies rod and cones
**Outer plexiform**
Inner Nuclear
Inner Plexiform
Ganglion cell layer
Optic nerve fibers
Inner Limmeting membrane
Outer Plexiform Layer:
− white matter
− synapses between photoreceptors and **bipolar/horizonal cells**
247
**Layers of the retina**
RPE
Photoreceptor
Outer limiting membrane
Cell bodies rod and cones
Outer plexiform
**Inner Nuclear**
Inner Plexiform
Ganglion cell layer
Optic nerve fibers
Inner Limmeting membrane
**Inner Nuclear Layer:**
**− horizontal cells**
o lateral circuit neurons
o closets to synaptic impute
**− bipolar cells**
o in the middle
**− amacrine cells**
o local circuit neurons
o closer inner plexiform layer
248
**Layers of the retina**
RPE
Photoreceptor
Outer limiting membrane
Cell bodies rod and cones
Outer plexiform
Inner Nuclear
**Inner Plexiform**
Ganglion cell layer
Optic nerve fibers
Inner Limmeting membrane
Inner Plexiform Layer:
− synapses between **bipolar/amacrine cells and ganglion cells**
249
**Layers of the retina**
RPE
Photoreceptor
Outer limiting membrane
Cell bodies rod and cones
Outer plexiform
Inner Nuclear
Inner Plexiform
**Ganglion cell layer**
Optic nerve fibers
Inner Limmeting membrane
**Ganglion cell axons**: course to disc
**Papillomacular bundle**
From macula to disc
Shorter fibers and deeper (closer to cell bodies)
**Superior & inferior arch** around macula Make arcuate patterns
**Tempora**l fibers don’t cross raphe
**Nasal** “radiating” go directly to disc
Long ones from peripheral retina more vitread Farther from cell bodies
250
5 Cell types of the Retina
**Amacrine:**
− make synaptic connections between bipolar and ganglion cells
**Horizontal:**
− make synaptic connection between bipolar and photoreceptor cells
**Bipolar:**
− connect photoreceptors to ganglion cells
**Mueller:**
− glial cells
− s**pecial oligodendrocytes**
− Attachment point for collagen II of vitreous
**− Polarized**
− Microvilli project into subretinal space
− True basement membrane end feet synthesize ILM
− OLM not BM: Zonula adherens between Mueller’s, rod & cone, fenestrated
(Permeable to fluid; does not form a barrier)
Interplexiform:
− synapse in both inner and outer plexiform layer
251
Central retina
**• Macula**
• 5.5mm diameter
**• Temporal to optic disc**
• Distinguishing feature= presence of xanthophylls pigment in plexiform layers
**• Macula lutea:**
– located 3.5mm lateral to edge of disk
**– Darkened region**
– Lutein & zeaxanthin pigments
**– Darker & taller RPE cells**
Foveola→fovea →parafovea→perifovea→ (end of macula) peripheral retina
252
Foveola
o **Foveola:**
− in the very center
− edge marked by sloped wall called **clivus**
**− avascular**
− **densest population of cones** with smallest diameter
253
Peripheral Retina
**o Peripheral Retina:**
− thins out
− **Rods and cones disappear**
− **nuclear & plexiform** layers **merge**
− Becomes **nonpigmented epithelium of pars plana** (single layer of
cuboid/columnar cells)
− Only a few blood vessels
ILM spined
− Retina attached to vitreous posterior to the ora serrata
254
Optic Nerve
Optic nerve:
o Extension of the brain (CNS)
o Composed of **ganglion cell axons
exits through lamina cribrosa**→**LGN**→**visual cortex**
o **Papillo macular bundle:** fibers that takes the shortest path from the macula to
the disc, deepest (closer to cell bodies)
o **Further from the disk**, fibers are more superficial
o Fibers radiate superiorly and inferiorly making an arcuate pattern
o **Raphe: horizontal line** superior and inferior fibers do not cross on the temporal
side
o **Nasals side** they go directly to the disk since fovea is not in the way
• Myelinated optic nerve and central retinal artery surrounded by meninges CT
(Pia, arachnoid, dura)
255
Optic nerve head
**Nerve head (optic disc)**
• **Elongated vertically**
• Physiologic Cup
o Difference in **cup to disk ratio in glaucoma**
• **Paler in color; no RPE**
o Lamina cribrosa and capillaries give yellow color
• **Physiologic blind spot**
• Site of entry of central retinal artery, exit retinal vein
256
Liver **Functions**
**second largest organ in body**
Functions:
• **Nutrients** (except lipids) are absorbed in intestine
• go **via portal vein to liver**
• processed and glycogen stored
o **Glycogen storage makes cells eosinophilic**
• Neutralizes and eliminates toxins
• Bile is exocrine secretion
• Makes **plasma protein**s such as **albumin**
257
Main cell type making up Liver
Hepatocyte
microvilli
**Polyhedral shape** in units called **lobules**
**Extensive rough and smooth ER for detox**
**Basolateral** surface in contact with **space of disse**
**Apical side** in contact with surface of other **hepatocytes**
## Footnote
o form plates
o make boundary of tubular space = **bile canaliculus**
o gap junction and tight junctions
258
Kupffer Cells
Ito Cells
**Kupffer cells**
In sinusoids on lumen surface
15% of surface
**Special monocytes** (macrophages)
o **Metabolize aged RBCs**
o **Digest hemoglobin**
o Secrete immuno proteins
o Destroy bacteria
**Ito (stellate) cells**
**In space of Disse**
**Fat storage**
**retinoid synthesis**
release (vit A metabolism)
259
Clinical Significance
Alcoholism
**Alcoholism**
Liver is the site of **alcohol dehydrogenases oxidize** EtOH
## Footnote
STAGES of Alcoholism
**o Fatty liver**
Reversible
**o Steatohepatitis**
pathological fatty liver - Accompanied by inflammation in cells
**o Cirrhosis**
Collagen proliferation in Space of Disse
Blocks space
**o Hepatocellular carcinoma**
260
GallBladder
Gallbladder
• Stores, concentrates and releases bile
• Connected to **cyctic duct**, which connects to the common **hepatic duct into duodenum**
o liver gallbladder and pancreas release products together
• Pear-shaped
261
Cells of the Gallbladder
**• Mucosa**
o Columnar
o many microvilli absorb water from bile concentrate
o Branching folds
**• Muscularis**
o Interlacing smooth muscle
o Contraction moves bile into cystic duct
o “spiral valve of Heister” controls opening into gallbladder
**• Serosa**
o outer layer; continuous with mesothelium lining liver
