Skin + blood components

Integument - Skin

Ectoderm → Epidermis Mesenchyme → Dermis

Ectoderm

Single layer - Simple Cuboidal Epithelium

Flattened cells

involved in exchange between the basal layer and the amniotic fluid

Basal layer

(stratum germinativum, stratum basale) - Stem Cells of epidermis

what specific skin layers do a needle taking blood pass through?

Stratum corneum → stratum granulosum → stratum spinosum → stratum basale

stratum lucidum

a thin, transparent layer of dead skin cells found in the epidermis of thick skin, specifically on the palms of the hands and soles of the feet. It sits between the stratum granulosum and the outermost stratum corneum

Stratum Basale

Stem Cells, only active mitotic layer, cells go through mitosis

Stratum Spinosum

Keratin produced in cytoplasm - Keratinocytes

Melanoma

Cancer of melanocyte - deadly skin cancer

Basal Cell Carcinoma – BCC

most common cancer – high cure rate

** PT CASE: WW2, no uv protection for hours, actin keratosis → Bcc

every cell has…

a basal and apical surface

Merocrine

a type of secretion or gland where cells release their products (like sweat or saliva) through exocytosis without any cellular damage or loss of structure

Holocrine secretion

a mode of glandular secretion in which the entire secretory cell ruptures and releases its contents into the glandular lumen, cell fills up and explodes

Sebaceous Gland:

Buds from the sides of developing hair follicles. Not all hair - some hairs lacks sebaceous glands. Branches to form several alveoli and ducts

Sebum - oily lubricant

Apocrine secretion

a mode of glandular secretion in which vesicles containing cellular material bud off from the apical (top) surface of the secretory cell and release their contents into the extracellular space, lumen

Apocrine glands-

Unbranched, highly coiled Associated with hair follicle

Function in sexual and social communication

Restricted to certain areas (Anogenital, Breasts)

Secretion begins at puberty

Eccrine secretion

the process by which eccrine sweat glands produce and release sweat onto the skin, directly across the plasma membrane

Eccrine gland

Solid unbranched epithelial downgrowth. Bud coils at tip to form secretory portion. Duct forms an attachment with epidermis. Central cells degenerate to from lumen. Secretory cells differentiate from cells lining duct. Myoepithelium from ectoderm, smooth muscle-like

Blood Composition

Fluid connective tissue

Plasma – non-living fluid matrix (~55%)

Formed elements – living blood "cells" suspended in plasma:

Erythrocytes (red blood cells, or RBCs) (~45%)

Leukocytes (white blood cells, or WBCs)

Platelets

Plasma

non-living fluid matrix (~55%)

 90% water

 Over 100 dissolved solutes

Nutrients, gases, hormones, wastes, proteins, inorganic ions

Formed elements

living blood "cells" suspended in plasma

 Only WBCs are complete cells

 RBCs are anucleate and have no other organelles

 Platelets are cell fragments

 Most formed elements survive in bloodstream only few days

 Most blood cells originate in bone marrow and do not divide

Numbers are always higher in…

Males- an average bigger males, females lose more blood

average Blood pH:

7.35-7.45

average blood volume:

5–6 L for males; 4–5 L for females

Functions of Blood:

Distribution - move nutrients and proteins around the body

Regulation - help regulate body temperature, ex. muscle contraction- blood moves toward the skin

Protection

Albumin

 60% of plasma protein

 Functions: Substance carrier and Blood buffer

Erythrocytes

 Biconcave discs, anucleate, essentially no organelles

 Diameters larger than some capillaries

 Filled with hemoglobin (Hb) for gas transport

 Major factor contributing to blood viscosity → blood clots

 Contain plasma membrane protein spectrin and other proteins

Spectrin provides flexibility to change shape

Hemoglobin binds reversibly with

oxygen

Hemoglobin Structure

 Globin composed of 4 polypeptide chains

 Two alpha and two beta chains

 Heme pigment bonded to each globin chain

Gives blood red color

Hematopoiesis

 Blood cell formation in red bone marrow

Composed of reticular connective tissue and blood sinusoids

 In adult, found in axial skeleton, girdles, and proximal epiphyses of humerus and femur

Hematopoietic stem cells (Hemocytoblasts)

Give rise to all formed elements

Hormones and growth factors push cell toward specific pathway of blood cell development

Committed cells cannot change

Reticulocyte

an immature red blood cell (RBC) that the bone marrow produces before it fully matures into a functional red blood cell, has a nucleus.

**If inc. reticulocyte → pt is bleeding and is making new blood cells

Hormonal Control of Erythropoiesis

Hormone Erythropoietin (EPO)

Direct stimulus for erythropoiesis

Always small amount in blood to maintain basal rate

iron

 Stored in cells as ferritin and hemosiderin

 Transported in blood bound to protein transferrin

Anemia

Blood has abnormally low O2-carrying capacity

Sign rather than disease itself

Blood O2 levels cannot support normal metabolism

Accompanied by fatigue, pallor, shortness of breath, and chills

Thalassemias

Typically Mediterranean ancestry

One or more globin chain(s) absent or faulty

RBCs thin, delicate, deficient in Hb

Many subtypes

Severity from mild to severe

Sickle-cell anemia

Hemoglobin S → lead to sickling

One amino acid wrong in a globin beta chain

RBCs crescent shaped when unload O2 or blood O2 low

RBCs rupture easily and block small vessels

Poor O2 delivery; pain

Sickle-cell gene

Two copies → Sickle-cell anemia

One copy → Sickle-cell trait; milder disease; better chance to survive malaria

ischemia

hypoxia + vascular issue

Preventing sickling

 Hydroxyurea induces fetal hemoglobin (Hemoglobin F, which does not sickle) formation

 Blocking RBC ion channels

 Stem cell transplants

 Gene therapy

function of the spleen

to clean blood

pt case: sickle cell anemia

• generalized pain that comes and goes

• ct. abd. scan shows no spleen

• no current/ historical dx.

  • sickle cell anemia, therefore needs Hemoglobin F

Leukocytes

carry O2 and CO2

 Function in defense against disease

Can leave capillaries via diapedesis

Move through tissue spaces by ameboid motion and positive chemotaxis

diapedesis

the process by which blood cells, particularly white blood cells (leukocytes), pass through the wall of a capillary and into the surrounding tissue to reach a site of infection or inflammation

chemotaxis

chemical mediator, the process by which white blood cells (leukocytes) migrate towards a chemical signal,

Leukocytosis

high count of WBCs, Normal response to infection

Vasodilation

the process by which blood vessels widen, increasing blood flow

Leukocytes abundance in blood

neutrophils, lymphocytes, monocytes, eosinophils, basophils

Neutrophils

 Most numerous WBCs

 Very phagocytic—"bacteria slayers"

histamine

inflammatory chemical that acts as vasodilator to attract WBCs to inflamed sites

Basophils

 Rarest WBCs

 Large, purplish-black (basophilic) granules contain histamine

Two types of Lymphocytes:

T lymphocytes (T cells) act against virus- infected cells and tumor cells

B lymphocytes (B cells) give rise to plasma cells, which produce antibodies

T lymphocytes (T cells)

act against virus- infected cells and tumor cells

B lymphocytes (B cells)

give rise to plasma cells, which produce antibodies

T killer cells

a type of lymphocyte that directly kills cells infected by viruses or that have become cancerous

Natural Killer cells

white blood cells (lymphocyte) that destroy infected and diseased cells, like cancer cells

Monocytes

Leave circulation, enter tissues, and differentiate into macrophages

macrophages

Actively phagocytic cells; crucial against viruses, intracellular bacterial parasites, and chronic infections

Infectious Mononucleosis

 Highly contagious viral disease

Epstein-Barr virus

 High numbers atypical agranulocytes

 Symptoms

Tired, achy, chronic sore throat, low fever

 Runs course with rest

Platelets

 Cytoplasmic fragments of megakaryocytes