The papillary and reticular dermis are the two layers of the dermis. They are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer.
Reticular Layer
Underlying the papillary layer is the much thicker reticular layer, composed of dense, irregular connective...

Phylum Ascomycota, a major division within the subkingdom Dikarya, comprises a diverse range of fungal species, including both unicellular yeasts and filamentous molds such as Aspergillus and Penicillium. These fungi thrive in a variety of habitats, from aquatic ecosystems to terrestrial environments, playing crucial ecological and economic roles.Morphology and ReproductionThe defining characteristic of Ascomycetes, commonly referred to as sac fungi, is the ascus—a sac-like structure that...

Zygomycota, previously classified as a distinct fungal group, are primarily terrestrial, saprophytic molds that play a crucial role as decomposers. Recent phylogenetic studies have revealed that these fungi are now divided into two major clades — Mucoromycota, which includes many symbiotic species, and Zoopagomycota, which primarily consists of parasitic and pathogenic fungi. These groups exhibit distinct ecological roles and reproductive strategies while sharing key structural and...

Basidiomycota is a diverse phylum of fungi that includes ecologically significant decomposers such as white rot fungi, symbionts like mycorrhizal fungi, plant pathogens such as rusts and smuts, and edible species like Agaricus bisporus (the common button mushroom). These fungi play crucial roles in nutrient cycling, symbiotic relationships, and even human health. Their defining feature is the basidium, a microscopic club-shaped structure responsible for producing basidiospores.Fruiting Bodies...

Seedless Vascular Plants Were the First Tall Plants on Earth

Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...